Pub Date : 2023-03-21eCollection Date: 2023-01-01DOI: 10.1093/function/zqad012
Adam J Amorese, Everett C Minchew, Michael D Tarpey, Andrew T Readyoff, Nicholas C Williamson, Cameron A Schmidt, Shawna L McMillin, Emma J Goldberg, Zoe S Terwilliger, Quincy A Spangenburg, Carol A Witczak, Jeffrey J Brault, E Dale Abel, Joseph M McClung, Kelsey H Fisher-Wellman, Espen E Spangenburg
The various functions of skeletal muscle (movement, respiration, thermogenesis, etc.) require the presence of oxygen (O2). Inadequate O2 bioavailability (ie, hypoxia) is detrimental to muscle function and, in chronic cases, can result in muscle wasting. Current therapeutic interventions have proven largely ineffective to rescue skeletal muscle from hypoxic damage. However, our lab has identified a mammalian skeletal muscle that maintains proper physiological function in an environment depleted of O2. Using mouse models of in vivo hindlimb ischemia and ex vivo anoxia exposure, we observed the preservation of force production in the flexor digitorum brevis (FDB), while in contrast the extensor digitorum longus (EDL) and soleus muscles suffered loss of force output. Unlike other muscles, we found that the FDB phenotype is not dependent on mitochondria, which partially explains the hypoxia resistance. Muscle proteomes were interrogated using a discovery-based approach, which identified significantly greater expression of the transmembrane glucose transporter GLUT1 in the FDB as compared to the EDL and soleus. Through loss-and-gain-of-function approaches, we determined that GLUT1 is necessary for the FDB to survive hypoxia, but overexpression of GLUT1 was insufficient to rescue other skeletal muscles from hypoxic damage. Collectively, the data demonstrate that the FDB is uniquely resistant to hypoxic insults. Defining the mechanisms that explain the phenotype may provide insight towards developing approaches for preventing hypoxia-induced tissue damage.
{"title":"Hypoxia Resistance Is an Inherent Phenotype of the Mouse Flexor Digitorum Brevis Skeletal Muscle.","authors":"Adam J Amorese, Everett C Minchew, Michael D Tarpey, Andrew T Readyoff, Nicholas C Williamson, Cameron A Schmidt, Shawna L McMillin, Emma J Goldberg, Zoe S Terwilliger, Quincy A Spangenburg, Carol A Witczak, Jeffrey J Brault, E Dale Abel, Joseph M McClung, Kelsey H Fisher-Wellman, Espen E Spangenburg","doi":"10.1093/function/zqad012","DOIUrl":"10.1093/function/zqad012","url":null,"abstract":"<p><p>The various functions of skeletal muscle (movement, respiration, thermogenesis, etc.) require the presence of oxygen (O<sub>2</sub>). Inadequate O<sub>2</sub> bioavailability (ie, hypoxia) is detrimental to muscle function and, in chronic cases, can result in muscle wasting. Current therapeutic interventions have proven largely ineffective to rescue skeletal muscle from hypoxic damage. However, our lab has identified a mammalian skeletal muscle that maintains proper physiological function in an environment depleted of O<sub>2</sub>. Using mouse models of <i>in vivo</i> hindlimb ischemia and <i>ex vivo</i> anoxia exposure, we observed the preservation of force production in the flexor digitorum brevis (FDB), while in contrast the extensor digitorum longus (EDL) and soleus muscles suffered loss of force output. Unlike other muscles, we found that the FDB phenotype is not dependent on mitochondria, which partially explains the hypoxia resistance. Muscle proteomes were interrogated using a discovery-based approach, which identified significantly greater expression of the transmembrane glucose transporter GLUT1 in the FDB as compared to the EDL and soleus. Through loss-and-gain-of-function approaches, we determined that GLUT1 is necessary for the FDB to survive hypoxia, but overexpression of GLUT1 was insufficient to rescue other skeletal muscles from hypoxic damage. Collectively, the data demonstrate that the FDB is uniquely resistant to hypoxic insults. Defining the mechanisms that explain the phenotype may provide insight towards developing approaches for preventing hypoxia-induced tissue damage.</p>","PeriodicalId":73119,"journal":{"name":"Function (Oxford, England)","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2023-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_pdf/80/55/zqad012.PMC10165545.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10130679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-23eCollection Date: 2023-01-01DOI: 10.1093/function/zqad009
Philip C Calder
Omega-3 (ω-3) polyunsaturated fatty acids (PUFAs) are a family of fatty acids distinguished by the presence of the double bond closest to the methyl terminus of the acyl chain being on carbon number 3 counting from the methyl terminal carbon. There are several members of the ω-3 PUFA family. Usually, the most common ω-3 PUFA in the human diet is α-linolenic acid (ALA; 18:3ω-3), an essential fatty acid made in plants from the ω-6 PUFA linoleic acid (LA; 18:2ω-3) by an enzymatic conversion catalyzed by delta-15 desaturase (Figure 1). Animals do not possess the latter enzyme, so they cannot make ALA. Nevertheless, once consumed in the diet, ALA can be converted by animals into long-chain, more unsaturated ω-3 PUFAs, including eicosapentaenoic acid (EPA; 20:5ω-3), docosapentaenoic acid (DPA; 22:5ω-3), and docosahexaenoic acid (DHA: 22:6ω-3) (Figure 1). EPA and DHA are biologically active, influencing cell membrane structure, intracellular signaling pathways, gene expression, and lipid mediator synthesis.1 DPA is less well studied but seems to have similar actions to EPA and DHA. Amongst dietary sources, EPA and DHA are found in the highest amounts in fatty fish; they are also present in fish oil-type supplements. EPA and DHA are linked to many health benefits, including reducing the risk of cardiovascular disease and mortality2; these effects are due to beneficial modification of a number of risk factors.3 There is also evidence that EPA and DHA might reduce the risk of developing nonalcoholic fatty liver disease, through effects on hepatic carbohydrate and fat metabolism and on inflammation.4 In general, case-control studies and longitudinal cohort studies provide stronger evidence for the benefits of EPA and DHA on disease outcomes, with findings from randomized controlled trials in patients at risk of, or already with, disease being inconsistent. Circulating and cell and tissue EPA, DPA, and DHA could come directly from the diet or from endogenous biosynthesis starting with ALA as substrate and using the pathway shown in Figure 1. In people with very low or no intake of seafood and not using supplements that contain EPA, DPA, and DHA, it seems likely that much of the body’s EPA, DPA, and DHA are produced through endogenous biosynthesis.5 Thus, a major role of ALA is as a precursor to its more bioactive ω-3 PUFA derivatives. Endogenous biosynthesis is likely to be downregulated when there is more EPA, DPA, and DHA in the diet.6 However, the relative contributions of diet and endogenous biosynthesis to EPA, DPA, and DHA levels in any compartment or pool within the body are not known. Furthermore, whether the origin of these fatty acids affects their biological action is not well studied. A recent paper published in Function starts to address these questions using murine models.7 Daniel et al.7 use wild-type C57Bl/6 mice and fat-1 mice. The latter are transgenic mice expressing the fat-1 gene from Caenorhabditis elegans, which encodes an enzyme with
{"title":"Do Endogenously Produced and Dietary ω-3 Fatty Acids Act Differently?","authors":"Philip C Calder","doi":"10.1093/function/zqad009","DOIUrl":"10.1093/function/zqad009","url":null,"abstract":"Omega-3 (ω-3) polyunsaturated fatty acids (PUFAs) are a family of fatty acids distinguished by the presence of the double bond closest to the methyl terminus of the acyl chain being on carbon number 3 counting from the methyl terminal carbon. There are several members of the ω-3 PUFA family. Usually, the most common ω-3 PUFA in the human diet is α-linolenic acid (ALA; 18:3ω-3), an essential fatty acid made in plants from the ω-6 PUFA linoleic acid (LA; 18:2ω-3) by an enzymatic conversion catalyzed by delta-15 desaturase (Figure 1). Animals do not possess the latter enzyme, so they cannot make ALA. Nevertheless, once consumed in the diet, ALA can be converted by animals into long-chain, more unsaturated ω-3 PUFAs, including eicosapentaenoic acid (EPA; 20:5ω-3), docosapentaenoic acid (DPA; 22:5ω-3), and docosahexaenoic acid (DHA: 22:6ω-3) (Figure 1). EPA and DHA are biologically active, influencing cell membrane structure, intracellular signaling pathways, gene expression, and lipid mediator synthesis.1 DPA is less well studied but seems to have similar actions to EPA and DHA. Amongst dietary sources, EPA and DHA are found in the highest amounts in fatty fish; they are also present in fish oil-type supplements. EPA and DHA are linked to many health benefits, including reducing the risk of cardiovascular disease and mortality2; these effects are due to beneficial modification of a number of risk factors.3 There is also evidence that EPA and DHA might reduce the risk of developing nonalcoholic fatty liver disease, through effects on hepatic carbohydrate and fat metabolism and on inflammation.4 In general, case-control studies and longitudinal cohort studies provide stronger evidence for the benefits of EPA and DHA on disease outcomes, with findings from randomized controlled trials in patients at risk of, or already with, disease being inconsistent. Circulating and cell and tissue EPA, DPA, and DHA could come directly from the diet or from endogenous biosynthesis starting with ALA as substrate and using the pathway shown in Figure 1. In people with very low or no intake of seafood and not using supplements that contain EPA, DPA, and DHA, it seems likely that much of the body’s EPA, DPA, and DHA are produced through endogenous biosynthesis.5 Thus, a major role of ALA is as a precursor to its more bioactive ω-3 PUFA derivatives. Endogenous biosynthesis is likely to be downregulated when there is more EPA, DPA, and DHA in the diet.6 However, the relative contributions of diet and endogenous biosynthesis to EPA, DPA, and DHA levels in any compartment or pool within the body are not known. Furthermore, whether the origin of these fatty acids affects their biological action is not well studied. A recent paper published in Function starts to address these questions using murine models.7 Daniel et al.7 use wild-type C57Bl/6 mice and fat-1 mice. The latter are transgenic mice expressing the fat-1 gene from Caenorhabditis elegans, which encodes an enzyme with ","PeriodicalId":73119,"journal":{"name":"Function (Oxford, England)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10165544/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9479233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-16eCollection Date: 2023-01-01DOI: 10.1093/function/zqad008
Brittni N Moore, Jennifer L Pluznick
{"title":"BMAL1 in the Adrenal Gland: It's About Time-A Perspective on \"Adrenal-Specific KO of the Circadian Clock Protein BMAL1 Alters Blood Pressure Rhythm and Timing of Eating Behavior\".","authors":"Brittni N Moore, Jennifer L Pluznick","doi":"10.1093/function/zqad008","DOIUrl":"10.1093/function/zqad008","url":null,"abstract":"","PeriodicalId":73119,"journal":{"name":"Function (Oxford, England)","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9972345/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9115352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-12eCollection Date: 2023-01-01DOI: 10.1093/function/zqad003
Cristoforo Silvestri, Vincenzo Di Marzo
{"title":"The Gut Microbiome-Endocannabinoidome Axis: A New Way of Controlling Metabolism, Inflammation, and Behavior.","authors":"Cristoforo Silvestri, Vincenzo Di Marzo","doi":"10.1093/function/zqad003","DOIUrl":"10.1093/function/zqad003","url":null,"abstract":"","PeriodicalId":73119,"journal":{"name":"Function (Oxford, England)","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2023-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9909364/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10799506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-09eCollection Date: 2023-01-01DOI: 10.1093/function/zqad001
Hannah M Costello, G Ryan Crislip, Kit-Yan Cheng, I Jeanette Lynch, Alexandria Juffre, Phillip Bratanatawira, Annalisse Mckee, Ryanne S Thelwell, Victor M Mendez, Charles S Wingo, Lauren G Douma, Michelle L Gumz
Brain and muscle ARNT-like 1 (BMAL1) is a core circadian clock protein and transcription factor that regulates many physiological functions, including blood pressure (BP). Male global Bmal1 knockout (KO) mice exhibit ∼10 mmHg reduction in BP, as well as a blunting of BP rhythm. The mechanisms of how BMAL1 regulates BP remains unclear. The adrenal gland synthesizes hormones, including glucocorticoids and mineralocorticoids, that influence BP rhythm. To determine the role of adrenal BMAL1 on BP regulation, adrenal-specific Bmal1 (ASCre/+ ::Bmal1) KO mice were generated using aldosterone synthase Cre recombinase to KO Bmal1 in the adrenal gland zona glomerulosa. We confirmed the localization and efficacy of the KO of BMAL1 to the zona glomerulosa. Male ASCre/+ ::Bmal1 KO mice displayed a shortened BP and activity period/circadian cycle (typically 24 h) by ∼1 h and delayed peak of BP and activity by ∼2 and 3 h, respectively, compared with littermate Cre- control mice. This difference was only evident when KO mice were in metabolic cages, which acted as a stressor, as serum corticosterone was increased in metabolic cages compared with home cages. AS Cre/+ ::Bmal1 KO mice also displayed altered diurnal variation in serum corticosterone. Furthermore, these mice have altered eating behaviors where they have a blunted night/day ratio of food intake, but no change in overall food consumed compared with controls. Overall, these data suggest that adrenal BMAL1 has a role in the regulation of BP rhythm and eating behaviors.
{"title":"Adrenal-Specific KO of the Circadian Clock Protein BMAL1 Alters Blood Pressure Rhythm and Timing of Eating Behavior.","authors":"Hannah M Costello, G Ryan Crislip, Kit-Yan Cheng, I Jeanette Lynch, Alexandria Juffre, Phillip Bratanatawira, Annalisse Mckee, Ryanne S Thelwell, Victor M Mendez, Charles S Wingo, Lauren G Douma, Michelle L Gumz","doi":"10.1093/function/zqad001","DOIUrl":"10.1093/function/zqad001","url":null,"abstract":"<p><p>Brain and muscle ARNT-like 1 (BMAL1) is a core circadian clock protein and transcription factor that regulates many physiological functions, including blood pressure (BP). Male global <i>Bmal1</i> knockout (KO) mice exhibit ∼10 mmHg reduction in BP, as well as a blunting of BP rhythm. The mechanisms of how BMAL1 regulates BP remains unclear. The adrenal gland synthesizes hormones, including glucocorticoids and mineralocorticoids, that influence BP rhythm. To determine the role of adrenal BMAL1 on BP regulation, adrenal-specific <i>Bmal1</i> (<i>AS<sup>Cre/+</sup></i> ::<i>Bmal1</i>) KO mice were generated using aldosterone synthase Cre recombinase to KO <i>Bmal1</i> in the adrenal gland zona glomerulosa. We confirmed the localization and efficacy of the KO of BMAL1 to the zona glomerulosa. Male <i>AS<sup>Cre/+</sup></i> ::<i>Bmal1</i> KO mice displayed a shortened BP and activity period/circadian cycle (typically 24 h) by ∼1 h and delayed peak of BP and activity by ∼2 and 3 h, respectively, compared with littermate Cre- control mice. This difference was only evident when KO mice were in metabolic cages, which acted as a stressor, as serum corticosterone was increased in metabolic cages compared with home cages. <i>A</i>S <i><sup>Cre/+</sup></i> ::<i>Bmal1</i> KO mice also displayed altered diurnal variation in serum corticosterone. Furthermore, these mice have altered eating behaviors where they have a blunted night/day ratio of food intake, but no change in overall food consumed compared with controls. Overall, these data suggest that adrenal BMAL1 has a role in the regulation of BP rhythm and eating behaviors.</p>","PeriodicalId":73119,"journal":{"name":"Function (Oxford, England)","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2023-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_pdf/20/c0/zqad001.PMC9909366.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10822439","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-06eCollection Date: 2023-01-01DOI: 10.1093/function/zqad002
Osama F Harraz
{"title":"Endothelial Cell Metabolism and Vascular Function: A Paradigm Shift?","authors":"Osama F Harraz","doi":"10.1093/function/zqad002","DOIUrl":"10.1093/function/zqad002","url":null,"abstract":"","PeriodicalId":73119,"journal":{"name":"Function (Oxford, England)","volume":null,"pages":null},"PeriodicalIF":5.1,"publicationDate":"2023-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ftp.ncbi.nlm.nih.gov/pub/pmc/oa_pdf/b4/d2/zqad002.PMC9909363.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10799993","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.1093/function/zqac072
Luis A Pardo
Ion channels remain fascinating molecular machines implicated in virtually every cellular function. Their activity can be studied in deep detail using biophysical techniques down to the single-molecule level. However, as large hydrophobic proteins embedded in a lipidic environment, their structure has traditionally been very difficult to study. Cryo-EM approaches have boosted our knowledge in the last few years, expanding the collection of resolved structures almost on a weekly basis. Yet, there are still open questions regarding the structure-function of the channels that are now starting to find answers. Ion channels react rapidly to a wide range of stimuli, opening a pathway for the flow of ions across the membrane. The coupling of the stimulus to the opening of the gate can be studied in ligand-gated channels by comparing the structures of the ligand-bound and unbound channels. Still, such a comparison is more difficult to achieve when the channel responds to physical rather than chemical stimuli, as is the case of voltage-gated channels. The molecular principles of voltage-dependent gating of ion channels have been known for four decades. The mechanism consists, in essence, of the movement of some parts of the protein (the voltage-sensing domains) relative to others. The displacement results in a conformational change that produces the opening of the gate, but the intimate molecular mechanisms linking both events remain only partly known in many cases. Although the problem might appear like an academic discussion for experts at first glance, it has many practical implications. On the one hand—mainly
{"title":"Watching Ion Channels on the Move.","authors":"Luis A Pardo","doi":"10.1093/function/zqac072","DOIUrl":"https://doi.org/10.1093/function/zqac072","url":null,"abstract":"Ion channels remain fascinating molecular machines implicated in virtually every cellular function. Their activity can be studied in deep detail using biophysical techniques down to the single-molecule level. However, as large hydrophobic proteins embedded in a lipidic environment, their structure has traditionally been very difficult to study. Cryo-EM approaches have boosted our knowledge in the last few years, expanding the collection of resolved structures almost on a weekly basis. Yet, there are still open questions regarding the structure-function of the channels that are now starting to find answers. Ion channels react rapidly to a wide range of stimuli, opening a pathway for the flow of ions across the membrane. The coupling of the stimulus to the opening of the gate can be studied in ligand-gated channels by comparing the structures of the ligand-bound and unbound channels. Still, such a comparison is more difficult to achieve when the channel responds to physical rather than chemical stimuli, as is the case of voltage-gated channels. The molecular principles of voltage-dependent gating of ion channels have been known for four decades. The mechanism consists, in essence, of the movement of some parts of the protein (the voltage-sensing domains) relative to others. The displacement results in a conformational change that produces the opening of the gate, but the intimate molecular mechanisms linking both events remain only partly known in many cases. Although the problem might appear like an academic discussion for experts at first glance, it has many practical implications. On the one hand—mainly","PeriodicalId":73119,"journal":{"name":"Function (Oxford, England)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9830534/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"10740532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.1093/function/zqad024
Camila Padilha, Ashleigh M Philp
; Hypoxias; r esistance; inher ent; phenotype; mouse Skeletal muscle is reliant on a constant oxygen supply for mov ement, cellular r espiration, and thermogenesis. Heter oge-neous fibre types exist in skeletal muscle as a continuum from slow- to fast-twitch to facilitate specialized function. Type I (oxidati v e fibr es) pr esent a slow-twitc h phenotype , c har acterized by high oxygen capacity and increased fatigue resistance. In contrast, type IIa (fast oxidati v e gl ycol ytic phenotype) and type IIx (fast gl ycol ytic) pr esent faster twitc h speeds and contr
{"title":"A Perspective on \"Hypoxia Resistance is an Inherent Phenotype of the Mouse Flexor Digitorum Brevis Skeletal Muscle\".","authors":"Camila Padilha, Ashleigh M Philp","doi":"10.1093/function/zqad024","DOIUrl":"https://doi.org/10.1093/function/zqad024","url":null,"abstract":"; Hypoxias; r esistance; inher ent; phenotype; mouse Skeletal muscle is reliant on a constant oxygen supply for mov ement, cellular r espiration, and thermogenesis. Heter oge-neous fibre types exist in skeletal muscle as a continuum from slow- to fast-twitch to facilitate specialized function. Type I (oxidati v e fibr es) pr esent a slow-twitc h phenotype , c har acterized by high oxygen capacity and increased fatigue resistance. In contrast, type IIa (fast oxidati v e gl ycol ytic phenotype) and type IIx (fast gl ycol ytic) pr esent faster twitc h speeds and contr","PeriodicalId":73119,"journal":{"name":"Function (Oxford, England)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10278979/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9713055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.1093/function/zqad027
Anna Boccaccio, Rocio K Finol-Urdaneta
pr otein-gated inw ardl y r ectifying potassium (GIRK, Kir3.x) hannels belong to the large family of inw ardl y r ectifying potasium (Kir) channels expressed throughout the body. Activation nd consequent opening of GIRK channels allow inward flow of otassium (K + ) ions into the cell resulting in membrane potenial hyperpolarization and decr eased excita bility. Thus, GIRK hannels play a key role in regulating the activity of neurons and ontrolling important physiological processes including neuonal excita bility, heart r ate , and pain per ception. 1 GIRK channels are integral membrane proteins, existing s homoor heterotetr amers. Eac h monomer features two embrane-spanning helices (M1 and M2), a re-entrant P-loop or controlling ion permeation and selectivity, and extensive ntracellular aminoand carboxy-termini crucial for channel ating. Permeation is regulated by an inner helix gate formed y the M2 segments and a cytoplasmic G-loop gate. 1 Acti v ation of GIRK channels is mediated by the direct interction of G βγ subunits, released from various G protein-coupled ece ptors (GPCRs) upon the acti v ation of inhibitory neuroransmitter r ece ptors. Howev er, the acti vity of GIRK channels epends on the presence of the membrane anionic phospholipid hosphatidylinositol-4,5-bisphosphate (PI(4,5)P 2 or PIP 2 ) while it s also modulated by ubiquitously present sodium (Na + ) ions. urthermore , GIRK c hannels ar e too r e gulated by c holesterol, hosphorylation, ethanol, etcetera. 1 The crystal structures of ecombinant GIRK channels have offered valuable insights into ow they are functionally regulated by various ligands. Thus, hannel opening is facilitated by PIP 2 at the plasma membrane, hereas G βγ and Na + modulate the c hannel’s inter action with IP 2 through conformational changes that govern the gating proess. 2 The intracellular milieu is a reducing environment charcterized by a balanced redox state. This state is crucial to upport cellular processes while serving as a pr otecti v e shield
{"title":"Redox Bridling of GIRK Channel Activity.","authors":"Anna Boccaccio, Rocio K Finol-Urdaneta","doi":"10.1093/function/zqad027","DOIUrl":"https://doi.org/10.1093/function/zqad027","url":null,"abstract":"pr otein-gated inw ardl y r ectifying potassium (GIRK, Kir3.x) hannels belong to the large family of inw ardl y r ectifying potasium (Kir) channels expressed throughout the body. Activation nd consequent opening of GIRK channels allow inward flow of otassium (K + ) ions into the cell resulting in membrane potenial hyperpolarization and decr eased excita bility. Thus, GIRK hannels play a key role in regulating the activity of neurons and ontrolling important physiological processes including neuonal excita bility, heart r ate , and pain per ception. 1 GIRK channels are integral membrane proteins, existing s homoor heterotetr amers. Eac h monomer features two embrane-spanning helices (M1 and M2), a re-entrant P-loop or controlling ion permeation and selectivity, and extensive ntracellular aminoand carboxy-termini crucial for channel ating. Permeation is regulated by an inner helix gate formed y the M2 segments and a cytoplasmic G-loop gate. 1 Acti v ation of GIRK channels is mediated by the direct interction of G βγ subunits, released from various G protein-coupled ece ptors (GPCRs) upon the acti v ation of inhibitory neuroransmitter r ece ptors. Howev er, the acti vity of GIRK channels epends on the presence of the membrane anionic phospholipid hosphatidylinositol-4,5-bisphosphate (PI(4,5)P 2 or PIP 2 ) while it s also modulated by ubiquitously present sodium (Na + ) ions. urthermore , GIRK c hannels ar e too r e gulated by c holesterol, hosphorylation, ethanol, etcetera. 1 The crystal structures of ecombinant GIRK channels have offered valuable insights into ow they are functionally regulated by various ligands. Thus, hannel opening is facilitated by PIP 2 at the plasma membrane, hereas G βγ and Na + modulate the c hannel’s inter action with IP 2 through conformational changes that govern the gating proess. 2 The intracellular milieu is a reducing environment charcterized by a balanced redox state. This state is crucial to upport cellular processes while serving as a pr otecti v e shield","PeriodicalId":73119,"journal":{"name":"Function (Oxford, England)","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10278978/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"9713057","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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