Qiushi Ye, Kathleen Joyce Carillo, Nicolas Delaeter, Lei Zhang, Jaekyun Jeon, Yanxin Liu
Sorcin, a penta-EF hand calcium-binding protein, is implicated in multidrug resistance (MDR) in various cancers and has roles in neurodegenerative diseases. It regulates cellular calcium homeostasis by interacting with calcium channels, pumps, and exchangers in a calcium-dependent manner. Calcium binding induces a conformational change in Sorcin, exposing hydrophobic surfaces that mediate protein interactions and calcium flux between the cytosol and endoplasmic reticulum. These exposed surfaces can also drive Sorcin aggregation in the absence of binding partners. Here, we exploited calcium-induced conformational changes and aggregation of Sorcin as a model to study its calcium sensitivity and aggregation mechanisms. Stopped-flow light scattering revealed that Sorcin aggregation is reversible, co-operative, and primarily influenced by Sorcin concentration rather than physiological calcium levels. Our findings suggest that the calcium sensitivity of Sorcin is finely tuned by its expression level, highlighting its role as an intracellular calcium sensor. This work establishes Sorcin as a model system for studying protein aggregation mechanisms with implications for MDR and neurodegenerative diseases.
{"title":"Kinetic investigation of calcium-induced Sorcin aggregation by stopped-flow light scattering.","authors":"Qiushi Ye, Kathleen Joyce Carillo, Nicolas Delaeter, Lei Zhang, Jaekyun Jeon, Yanxin Liu","doi":"10.1042/BCJ20253194","DOIUrl":"10.1042/BCJ20253194","url":null,"abstract":"<p><p>Sorcin, a penta-EF hand calcium-binding protein, is implicated in multidrug resistance (MDR) in various cancers and has roles in neurodegenerative diseases. It regulates cellular calcium homeostasis by interacting with calcium channels, pumps, and exchangers in a calcium-dependent manner. Calcium binding induces a conformational change in Sorcin, exposing hydrophobic surfaces that mediate protein interactions and calcium flux between the cytosol and endoplasmic reticulum. These exposed surfaces can also drive Sorcin aggregation in the absence of binding partners. Here, we exploited calcium-induced conformational changes and aggregation of Sorcin as a model to study its calcium sensitivity and aggregation mechanisms. Stopped-flow light scattering revealed that Sorcin aggregation is reversible, co-operative, and primarily influenced by Sorcin concentration rather than physiological calcium levels. Our findings suggest that the calcium sensitivity of Sorcin is finely tuned by its expression level, highlighting its role as an intracellular calcium sensor. This work establishes Sorcin as a model system for studying protein aggregation mechanisms with implications for MDR and neurodegenerative diseases.</p>","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":" ","pages":""},"PeriodicalIF":4.3,"publicationDate":"2025-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12687447/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145353536","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Parkinson's disease (PD) is a multisystem disorder presenting motor and non-motor symptoms. Motor dysfunction is the most debilitating, caused by the degeneration of dopamine-producing neurons. Increasing evidence indicates that synapse demise occurs years before neuronal death. Yet, the early synaptic dysfunctions in PD remain poorly understood. Leucine-Rich Repeat Kinase 2 (LRRK2), a serine/threonine kinase and GTPase relevant for both familial and sporadic forms of PD, has been increasingly associated with synaptic processes. These include the phosphorylation of key synaptic proteins and interactions with cytoskeletal components. Brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF) are fundamental for synapse maturation, maintenance, and plasticity. Recent findings indicate that neurotrophic signaling is impaired in PD. In this review, we critically discuss the significance of identifying and clarifying the early molecular events leading to synaptic dysfunction in PD. We examine how mutant LRRK2 affects these processes and the relationship between LRRK2 and BDNF signaling from both mechanistic and therapeutic perspectives.
{"title":"LRRK2 and the fragile synapse: a molecular prelude to Parkinson's disease?","authors":"Beatrice Masotti,Giulia Tombesi,Loukia Parisiadou,Elisa Greggio","doi":"10.1042/bcj20253351","DOIUrl":"https://doi.org/10.1042/bcj20253351","url":null,"abstract":"Parkinson's disease (PD) is a multisystem disorder presenting motor and non-motor symptoms. Motor dysfunction is the most debilitating, caused by the degeneration of dopamine-producing neurons. Increasing evidence indicates that synapse demise occurs years before neuronal death. Yet, the early synaptic dysfunctions in PD remain poorly understood. Leucine-Rich Repeat Kinase 2 (LRRK2), a serine/threonine kinase and GTPase relevant for both familial and sporadic forms of PD, has been increasingly associated with synaptic processes. These include the phosphorylation of key synaptic proteins and interactions with cytoskeletal components. Brain-derived neurotrophic factor (BDNF) and glial-derived neurotrophic factor (GDNF) are fundamental for synapse maturation, maintenance, and plasticity. Recent findings indicate that neurotrophic signaling is impaired in PD. In this review, we critically discuss the significance of identifying and clarifying the early molecular events leading to synaptic dysfunction in PD. We examine how mutant LRRK2 affects these processes and the relationship between LRRK2 and BDNF signaling from both mechanistic and therapeutic perspectives.","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"19 1","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145373846","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Autophagy is recognized as one of the two main intracellular recycling pathways that play an essential role in cellular homeostasis by maintaining accurate energy levels and carrying out quality control functions. One of the major autophagic mechanisms, the so-called macroautophagy, is involved in the lysosomal degradation of different cytoplasmic components, such as long-lived proteins and damaged or dysfunctional organelles. Numerous studies have demonstrated that participation of intracellular membrane trafficking events is key for the progression of autophagy. In this review, we will focus on the small GTPases of the RAS-related in brain protein family, which have a crucial role in vesicular transport.
{"title":"Vesicular transport in the autophagic route: RAB GTPases as pivotal regulators of autophagy.","authors":"Romina Abba,María Isabel Colombo","doi":"10.1042/bcj20253092","DOIUrl":"https://doi.org/10.1042/bcj20253092","url":null,"abstract":"Autophagy is recognized as one of the two main intracellular recycling pathways that play an essential role in cellular homeostasis by maintaining accurate energy levels and carrying out quality control functions. One of the major autophagic mechanisms, the so-called macroautophagy, is involved in the lysosomal degradation of different cytoplasmic components, such as long-lived proteins and damaged or dysfunctional organelles. Numerous studies have demonstrated that participation of intracellular membrane trafficking events is key for the progression of autophagy. In this review, we will focus on the small GTPases of the RAS-related in brain protein family, which have a crucial role in vesicular transport.","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"160 1","pages":"1531-1544"},"PeriodicalIF":4.1,"publicationDate":"2025-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145311709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rokas Juodeikis,Robert Ulrich,Charlea Clarke,Michal Banasik,Evelyne Deery,Gerhard Saalbach,Bernhard Kräutler,Simon R Carding,Michael A Geeves,Richard Pickersgill,Martin J Warren
Vitamin B12 (cobalamin) and related cobamides are essential cofactors for many gut bacteria, yet their acquisition requires complex uptake systems due to limited availability. In the human gut commensal Bacteroides thetaiotaomicron, cobamide uptake is mediated by multiple operons encoding outer membrane proteins, transporters and uncharacterised lipoproteins, some of which are incorporated into bacterial extracellular vesicles (BEVs). Here, we advance the functional and structural understanding of this cobamide acquisition system by examining previously uncharacterized features. Bioinformatic and promoter-reporter analyses revealed four uptake operons, including novel genes we designate btuK, btuJ, btuL and btuX, with evidence for internal promoters and riboswitch regulation. Recombinant expression and binding assays identified ten cobamide-binding proteins, including three novel lipoproteins (BtuK1, BtuJ1 and BtuJ2). Biophysical measurements demonstrated affinities in the nano- to picomolar range, with BtuJ proteins displaying exceptionally tight binding. High-resolution crystal structures of BtuJ1 and BtuJ2 revealed an augmented β-jelly-roll fold, with conserved tyrosine residues forming a "halo" around the corrin, suggesting a conserved binding mechanism within the IPR027828 protein family. Comparative proteomics of cells and BEVs under cobamide starvation showed selective enrichment of BtuJ and BtuL in BEVs. Functional assays demonstrated that BEV-mediated cobamide uptake depends specifically on BtuJ1 and BtuJ2, whereas BtuL promotes early-phase BEV release. These findings establish the BtuJ proteins as critical BEV-associated cobamide-binding components, provide structural insights into their tight binding, and suggest a model where BEVs act analogously to siderophores, capturing cobamides for delivery to cells. This work highlights the central role of BEVs in microbial nutrient competition.
{"title":"Extracellular Vesicle-Linked Vitamin B12 Acquisition via Novel Binding Proteins in Bacteroides thetaiotaomicron.","authors":"Rokas Juodeikis,Robert Ulrich,Charlea Clarke,Michal Banasik,Evelyne Deery,Gerhard Saalbach,Bernhard Kräutler,Simon R Carding,Michael A Geeves,Richard Pickersgill,Martin J Warren","doi":"10.1042/bcj20253340","DOIUrl":"https://doi.org/10.1042/bcj20253340","url":null,"abstract":"Vitamin B12 (cobalamin) and related cobamides are essential cofactors for many gut bacteria, yet their acquisition requires complex uptake systems due to limited availability. In the human gut commensal Bacteroides thetaiotaomicron, cobamide uptake is mediated by multiple operons encoding outer membrane proteins, transporters and uncharacterised lipoproteins, some of which are incorporated into bacterial extracellular vesicles (BEVs). Here, we advance the functional and structural understanding of this cobamide acquisition system by examining previously uncharacterized features. Bioinformatic and promoter-reporter analyses revealed four uptake operons, including novel genes we designate btuK, btuJ, btuL and btuX, with evidence for internal promoters and riboswitch regulation. Recombinant expression and binding assays identified ten cobamide-binding proteins, including three novel lipoproteins (BtuK1, BtuJ1 and BtuJ2). Biophysical measurements demonstrated affinities in the nano- to picomolar range, with BtuJ proteins displaying exceptionally tight binding. High-resolution crystal structures of BtuJ1 and BtuJ2 revealed an augmented β-jelly-roll fold, with conserved tyrosine residues forming a \"halo\" around the corrin, suggesting a conserved binding mechanism within the IPR027828 protein family. Comparative proteomics of cells and BEVs under cobamide starvation showed selective enrichment of BtuJ and BtuL in BEVs. Functional assays demonstrated that BEV-mediated cobamide uptake depends specifically on BtuJ1 and BtuJ2, whereas BtuL promotes early-phase BEV release. These findings establish the BtuJ proteins as critical BEV-associated cobamide-binding components, provide structural insights into their tight binding, and suggest a model where BEVs act analogously to siderophores, capturing cobamides for delivery to cells. This work highlights the central role of BEVs in microbial nutrient competition.","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"1 1","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145288476","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mitochondrial protein homeostasis depends mainly on the efficient import and folding of nuclear-encoded proteins, and defects in this process can lead to proteotoxicity, which is harmful to the cell. Mitochondrial chaperones and proteases are essential defense mechanisms that ensure dysfunctional proteins' proper concentration, folding, and degradation. Lon protease 1 (Pim1 in yeast) is the mitochondrial matrix protease known to prevent protein aggregation by degrading unfolded proteins. Here, we show that two essential components of ATP-dependent presequence translocase and associated motor (PAM complex)- Pam18 and Pam16 are specifically targeted for degradation by the proteolytically active Lon/Pim1, both in vitro and in vivo. Further, overexpression of Pam18 and Pam16 exacerbates the growth defect of the delta pim1 strain. Hence, our study reveals, for the first time, that components involved in protein import are substrates of Pim1, which could have potential implications for regulating mitochondrial protein import and proteostasis.
{"title":"Lon/Pim1 mediated degradation of presequence translocase-associated motor components Pam16 and Pam18 in Saccharomyces cerevisiae.","authors":"Yerranna Boggula,Arpan Chatterjee,Gaurav Simaiya,Amita Pal,Akash Srinivasan,Naresh Babu Sepuri","doi":"10.1042/bcj20243016","DOIUrl":"https://doi.org/10.1042/bcj20243016","url":null,"abstract":"Mitochondrial protein homeostasis depends mainly on the efficient import and folding of nuclear-encoded proteins, and defects in this process can lead to proteotoxicity, which is harmful to the cell. Mitochondrial chaperones and proteases are essential defense mechanisms that ensure dysfunctional proteins' proper concentration, folding, and degradation. Lon protease 1 (Pim1 in yeast) is the mitochondrial matrix protease known to prevent protein aggregation by degrading unfolded proteins. Here, we show that two essential components of ATP-dependent presequence translocase and associated motor (PAM complex)- Pam18 and Pam16 are specifically targeted for degradation by the proteolytically active Lon/Pim1, both in vitro and in vivo. Further, overexpression of Pam18 and Pam16 exacerbates the growth defect of the delta pim1 strain. Hence, our study reveals, for the first time, that components involved in protein import are substrates of Pim1, which could have potential implications for regulating mitochondrial protein import and proteostasis.","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"14 1","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145296275","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sophie J L Brown,David C Briggs,Patrick Costello,Hiroko Yaguchi,Charles R M Bangham,Peter J Parker,Neil Q McDonald
Mutations in the T-cell receptor signalling pathway have been identified in patients with adult T-cell leukaemia/lymphoma (ATLL) and one of the most frequently observed targets of these mutations is protein kinase C beta (PKCb). Here we have characterised the most frequent mutation in PKCb (D427N) addressing the issue of gain/loss of function, neomorphic change, assessing the impact of mutation in vivo, in cells, biochemically and structurally. It is concluded that this mutation is a gain-of-function, activating mutation that confers an altered substrate specificity on this protein kinase. In a constitutive knock-in mouse model this activated allele induces splenomegaly associated with extramedullary haematopoiesis. Pharmacologically, the D427N mutant protein displays poor sensitivity to established PKCb inhibitors, necessitating development of bespoke therapeutics for any ATLL intervention through this target. Such efforts could be guided by the availability the D427N mutant-ruboxistaurin structure presented here.
{"title":"Penetrant PKCb mutation in ATLL displays a mixed gain-of-function.","authors":"Sophie J L Brown,David C Briggs,Patrick Costello,Hiroko Yaguchi,Charles R M Bangham,Peter J Parker,Neil Q McDonald","doi":"10.1042/bcj20253384","DOIUrl":"https://doi.org/10.1042/bcj20253384","url":null,"abstract":"Mutations in the T-cell receptor signalling pathway have been identified in patients with adult T-cell leukaemia/lymphoma (ATLL) and one of the most frequently observed targets of these mutations is protein kinase C beta (PKCb). Here we have characterised the most frequent mutation in PKCb (D427N) addressing the issue of gain/loss of function, neomorphic change, assessing the impact of mutation in vivo, in cells, biochemically and structurally. It is concluded that this mutation is a gain-of-function, activating mutation that confers an altered substrate specificity on this protein kinase. In a constitutive knock-in mouse model this activated allele induces splenomegaly associated with extramedullary haematopoiesis. Pharmacologically, the D427N mutant protein displays poor sensitivity to established PKCb inhibitors, necessitating development of bespoke therapeutics for any ATLL intervention through this target. Such efforts could be guided by the availability the D427N mutant-ruboxistaurin structure presented here.","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"1 1","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145288401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Saccharomyces cerevisiae, a widely studied unicellular eukaryotic model, multiplies and divides through an asymmetric budding process, where a mother cell produces a smaller daughter cell. Although cells age across successive cell divisions, provided the mother is not too old, each daughter cell inherits a full lifespan potential. Extensive studies in budding yeast have established a framework for understanding how asymmetric cell division contributes to this lifespan resetting. One postulate of this framework is that the capacity of mother cells to bud daughters with full replicative potential is critically dependent on membraneassociated mechanisms that enable asymmetric inheritance of aging factors. Despite the identification of numerous asymmetrically distributed proteins, an integrated catalog detailing their roles in aging has not been compiled. This review provides a comprehensive resource of asymmetrically distributed membrane proteins in yeast that have a role in replicative aging. Existing knowledge governing the establishment and maintenance of asymmetry is synthesized, and gaps in our understanding of how membrane asymmetry contributes to cellular aging are identified.
{"title":"Cell membrane asymmetries and cellular aging.","authors":"Valentina Salzman,Pablo S Aguilar","doi":"10.1042/bcj20253265","DOIUrl":"https://doi.org/10.1042/bcj20253265","url":null,"abstract":"Saccharomyces cerevisiae, a widely studied unicellular eukaryotic model, multiplies and divides through an asymmetric budding process, where a mother cell produces a smaller daughter cell. Although cells age across successive cell divisions, provided the mother is not too old, each daughter cell inherits a full lifespan potential. Extensive studies in budding yeast have established a framework for understanding how asymmetric cell division contributes to this lifespan resetting. One postulate of this framework is that the capacity of mother cells to bud daughters with full replicative potential is critically dependent on membraneassociated mechanisms that enable asymmetric inheritance of aging factors. Despite the identification of numerous asymmetrically distributed proteins, an integrated catalog detailing their roles in aging has not been compiled. This review provides a comprehensive resource of asymmetrically distributed membrane proteins in yeast that have a role in replicative aging. Existing knowledge governing the establishment and maintenance of asymmetry is synthesized, and gaps in our understanding of how membrane asymmetry contributes to cellular aging are identified.","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"1 1","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145247106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Correction: Phosphoinositide 3-kinase-dependent phosphorylation of the dual adaptor for phosphotyrosine and 3-phosphoinositides by the Src family of tyrosine kinase.","authors":"","doi":"10.1042/BCJ3490605_COR","DOIUrl":"10.1042/BCJ3490605_COR","url":null,"abstract":"","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"482 20","pages":""},"PeriodicalIF":4.3,"publicationDate":"2025-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12687430/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145249483","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Colleen Sprigg,Hayley L Whitfield,Philip T Leftwich,Hui-Fen Kuo,Tzyy-Jen Chiou,Adolfo Saiardi,Megan L Shipton,Andrew M Riley,Barry V L Potter,Dawn Scholey,Emily Burton,Mike R Bedford,Charles A Brearley
Inositol phosphate (InsP) and diphosphoinositol phosphate (PP-InsP) analysis in tissues is plagued by multiple difficulties of sensitivity, regioisomer resolution and the need for radiolabeling with metabolic precursors. We describe a liquid chromatography (LC) inductively coupled plasma (ICP) mass spectrometry (MS) method (LC-ICP-MS) that addresses all such issues and use LC-ICP-MS to analyse InsPs in avian tissues. The highly sensitive technique tolerates complex matrices and, by powerful chromatography, resolves in a single run multiple non-enantiomeric myo-inositol tetrakisphosphates, myo-inositol pentakisphosphates and all inositol hexakisphosphates, including myo-inositol 1,2,3,4,5,6-hexakisphosphate (phytate), known in nature. It also separates and quantifies diphospho myo-inositol pentakisphosphate (PP-InsP5) isomers from their biological precursors and from 1,5-bis-diphospho myo-inositol 2,3,4,6 tetrakisphosphate (1,5-[PP]2-InsP4). Gut tissue inositol phosphates, belonging to a non-canonical, lipid-independent pathway, are shown to differ from phytate digestion products and to be responsive to diet.
{"title":"Phosphorus-specific, liquid chromatography inductively coupled plasma mass-spectrometry for analysis of inositol phosphate and inositol pyrophosphate metabolism.","authors":"Colleen Sprigg,Hayley L Whitfield,Philip T Leftwich,Hui-Fen Kuo,Tzyy-Jen Chiou,Adolfo Saiardi,Megan L Shipton,Andrew M Riley,Barry V L Potter,Dawn Scholey,Emily Burton,Mike R Bedford,Charles A Brearley","doi":"10.1042/bcj20253151","DOIUrl":"https://doi.org/10.1042/bcj20253151","url":null,"abstract":"Inositol phosphate (InsP) and diphosphoinositol phosphate (PP-InsP) analysis in tissues is plagued by multiple difficulties of sensitivity, regioisomer resolution and the need for radiolabeling with metabolic precursors. We describe a liquid chromatography (LC) inductively coupled plasma (ICP) mass spectrometry (MS) method (LC-ICP-MS) that addresses all such issues and use LC-ICP-MS to analyse InsPs in avian tissues. The highly sensitive technique tolerates complex matrices and, by powerful chromatography, resolves in a single run multiple non-enantiomeric myo-inositol tetrakisphosphates, myo-inositol pentakisphosphates and all inositol hexakisphosphates, including myo-inositol 1,2,3,4,5,6-hexakisphosphate (phytate), known in nature. It also separates and quantifies diphospho myo-inositol pentakisphosphate (PP-InsP5) isomers from their biological precursors and from 1,5-bis-diphospho myo-inositol 2,3,4,6 tetrakisphosphate (1,5-[PP]2-InsP4). Gut tissue inositol phosphates, belonging to a non-canonical, lipid-independent pathway, are shown to differ from phytate digestion products and to be responsive to diet.","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"22 1","pages":""},"PeriodicalIF":4.1,"publicationDate":"2025-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145235869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Immunotherapy relies on the targeting of immune checkpoint receptors and their respective ligands by specific antibodies that bind to the cell surface proteins. The pace of this highly successful clinical advancement has outstripped our cell biological understanding of these receptors. Here, we discuss what is known about their intracellular trafficking itineraries, which determine the bioavailability of these proteins for clinical targeting. Some of them are amongst the shortest-lived membrane proteins (CTLA-4), whilst others can be very stable (PD-L1). We highlight the ubiquitin system, which is key to determining their turnover, as it plays a key role in disposing of misfolded newly synthesised proteins via the ERAD pathway and generating a key signal for endosomal sorting towards lysosomes. In some cases, ubiquitylation can modulate the signalling function of the immune checkpoint receptor, as seen for LAG-3. Immune checkpoint proteins can evade lysosomal degradation by effective recycling to the plasma membrane using highly specialised factors, including CMTM6 (for PD-L1) and LRBA (for CTLA-4). Lastly, we consider how reprogramming the ubiquitin system emerges as an alternative modality in targeting immune checkpoint receptors.
{"title":"Proteostasis of immune checkpoint receptors.","authors":"Pei Yee Tey, Sylvie Urbé, Michael J Clague","doi":"10.1042/BCJ20253299","DOIUrl":"10.1042/BCJ20253299","url":null,"abstract":"<p><p>Immunotherapy relies on the targeting of immune checkpoint receptors and their respective ligands by specific antibodies that bind to the cell surface proteins. The pace of this highly successful clinical advancement has outstripped our cell biological understanding of these receptors. Here, we discuss what is known about their intracellular trafficking itineraries, which determine the bioavailability of these proteins for clinical targeting. Some of them are amongst the shortest-lived membrane proteins (CTLA-4), whilst others can be very stable (PD-L1). We highlight the ubiquitin system, which is key to determining their turnover, as it plays a key role in disposing of misfolded newly synthesised proteins via the ERAD pathway and generating a key signal for endosomal sorting towards lysosomes. In some cases, ubiquitylation can modulate the signalling function of the immune checkpoint receptor, as seen for LAG-3. Immune checkpoint proteins can evade lysosomal degradation by effective recycling to the plasma membrane using highly specialised factors, including CMTM6 (for PD-L1) and LRBA (for CTLA-4). Lastly, we consider how reprogramming the ubiquitin system emerges as an alternative modality in targeting immune checkpoint receptors.</p>","PeriodicalId":8825,"journal":{"name":"Biochemical Journal","volume":"482 19","pages":"1489-1516"},"PeriodicalIF":4.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12794375/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145197856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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