Jacob Malin, Christian Rosa Birriel, Sergio Astigarraga, J. Treisman, V. Hatini
Malin et al. show that the homophilic adhesion molecule Sidekick interacts alternately with the WAVE regulatory complex and with Polychaetoid/Zonula occludence-1 at tricellular adherens junctions to dynamically rebalance opposing protrusive and contractile forces that repeatedly expand and contract cell contacts to maintain cell–cell contacts and ensure proper epithelial remodeling.
{"title":"Sidekick dynamically rebalances contractile and protrusive forces to control tissue morphogenesis","authors":"Jacob Malin, Christian Rosa Birriel, Sergio Astigarraga, J. Treisman, V. Hatini","doi":"10.1083/jcb.202107035","DOIUrl":"https://doi.org/10.1083/jcb.202107035","url":null,"abstract":"Malin et al. show that the homophilic adhesion molecule Sidekick interacts alternately with the WAVE regulatory complex and with Polychaetoid/Zonula occludence-1 at tricellular adherens junctions to dynamically rebalance opposing protrusive and contractile forces that repeatedly expand and contract cell contacts to maintain cell–cell contacts and ensure proper epithelial remodeling.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117764782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Saranyaraajan Varadarajan, Shahana A Chumki, Rachel E. Stephenson, Eileen Misterovich, Jessica L. Wu, Claire E Dudley, I. Erofeev, A. Goryachev, Ann L. Miller
Varadarajan et al. find that calcium flashes regulate epithelial barrier function. Using live imaging, optogenetics, and laser-induced tight junction injury, they show that mechanosensitive channel-dependent calcium flashes promote sustained local activation of RhoA, allowing cells to repair tight junction leaks induced by mechanical stimuli.
{"title":"Mechanosensitive calcium flashes promote sustained RhoA activation during tight junction remodeling","authors":"Saranyaraajan Varadarajan, Shahana A Chumki, Rachel E. Stephenson, Eileen Misterovich, Jessica L. Wu, Claire E Dudley, I. Erofeev, A. Goryachev, Ann L. Miller","doi":"10.1083/jcb.202105107","DOIUrl":"https://doi.org/10.1083/jcb.202105107","url":null,"abstract":"Varadarajan et al. find that calcium flashes regulate epithelial barrier function. Using live imaging, optogenetics, and laser-induced tight junction injury, they show that mechanosensitive channel-dependent calcium flashes promote sustained local activation of RhoA, allowing cells to repair tight junction leaks induced by mechanical stimuli.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123983006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rebecca Cabral-Dias, Stefanie Lucarelli, Karolina Zak, Sadia Rahmani, Gurjeet Judge, John Abousawan, Laura F DiGiovanni, Dafne Vural, K. Anderson, Michael G. Sugiyama, G. Genç, W. Hong, R. Botelho, G. Fairn, P. Kim, C. Antonescu
Ligand binding to EGF receptor (EGFR) triggers signaling and concomitant receptor recruitment to clathrin-coated pits. This study reveals that the signaling adaptor TOM1L1 recruits Fyn to a specialized subset of clathrin-coated pits and is required for SHIP2 recruitment and regulation of Akt signaling by EGFR.
{"title":"Fyn and TOM1L1 are recruited to clathrin-coated pits and regulate Akt signaling","authors":"Rebecca Cabral-Dias, Stefanie Lucarelli, Karolina Zak, Sadia Rahmani, Gurjeet Judge, John Abousawan, Laura F DiGiovanni, Dafne Vural, K. Anderson, Michael G. Sugiyama, G. Genç, W. Hong, R. Botelho, G. Fairn, P. Kim, C. Antonescu","doi":"10.1083/jcb.201808181","DOIUrl":"https://doi.org/10.1083/jcb.201808181","url":null,"abstract":"Ligand binding to EGF receptor (EGFR) triggers signaling and concomitant receptor recruitment to clathrin-coated pits. This study reveals that the signaling adaptor TOM1L1 recruits Fyn to a specialized subset of clathrin-coated pits and is required for SHIP2 recruitment and regulation of Akt signaling by EGFR.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121164243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-26DOI: 10.1101/2022.02.26.482093
Jierui Zhao, Mai Thu Bui, Juncai Ma, Fabian Künzl, Lorenzo Picchianti, Juan Carlos De la Concepcion, Yixuan Chen, Sofia Petsangouraki, Azadeh Mohseni, M. García-León, Marta Salas Gomez, Caterina Giannini, Dubois Gwennogan, Roksolana Kobylinska, Marion Clavel, S. Schellmann, Y. Jaillais, J. Friml, Byungho Kang, Yasin F. Dagdas
Autophagosomes are double-membraned vesicles that traffic harmful or unwanted cellular macromolecules to the vacuole for recycling. Although autophagosome biogenesis has been extensively studied, mechanisms of autophagosome maturation, i.e., delivery and fusion with the vacuole, remain largely unknown in plants. Here, we have identified an autophagy adaptor, CFS1, that directly interacts with the autophagosome marker ATG8 and localizes on both membranes of the autophagosome. Autophagosomes form normally in Arabidopsis thaliana cfs1 mutants, but their delivery to the vacuole is disrupted. CFS1’s function is evolutionarily conserved in plants as it also localizes to the autophagosomes and plays a role in autophagic flux in the liverwort Marchantia polymorpha. CFS1 regulates autophagic flux by connecting autophagosomes with the ESCRT-I component VPS23, leading to the formation of amphisomes. Disrupting the VPS23-CFS1 interaction affects autophagic flux and renders plants sensitive to starvation stress. Altogether, our results reveal a deeply conserved mechanism of vacuolar delivery in plants that is mediated by amphisomes.
{"title":"Plant autophagosomes mature into amphisomes prior to their delivery to the central vacuole","authors":"Jierui Zhao, Mai Thu Bui, Juncai Ma, Fabian Künzl, Lorenzo Picchianti, Juan Carlos De la Concepcion, Yixuan Chen, Sofia Petsangouraki, Azadeh Mohseni, M. García-León, Marta Salas Gomez, Caterina Giannini, Dubois Gwennogan, Roksolana Kobylinska, Marion Clavel, S. Schellmann, Y. Jaillais, J. Friml, Byungho Kang, Yasin F. Dagdas","doi":"10.1101/2022.02.26.482093","DOIUrl":"https://doi.org/10.1101/2022.02.26.482093","url":null,"abstract":"Autophagosomes are double-membraned vesicles that traffic harmful or unwanted cellular macromolecules to the vacuole for recycling. Although autophagosome biogenesis has been extensively studied, mechanisms of autophagosome maturation, i.e., delivery and fusion with the vacuole, remain largely unknown in plants. Here, we have identified an autophagy adaptor, CFS1, that directly interacts with the autophagosome marker ATG8 and localizes on both membranes of the autophagosome. Autophagosomes form normally in Arabidopsis thaliana cfs1 mutants, but their delivery to the vacuole is disrupted. CFS1’s function is evolutionarily conserved in plants as it also localizes to the autophagosomes and plays a role in autophagic flux in the liverwort Marchantia polymorpha. CFS1 regulates autophagic flux by connecting autophagosomes with the ESCRT-I component VPS23, leading to the formation of amphisomes. Disrupting the VPS23-CFS1 interaction affects autophagic flux and renders plants sensitive to starvation stress. Altogether, our results reveal a deeply conserved mechanism of vacuolar delivery in plants that is mediated by amphisomes.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115122979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-02-11DOI: 10.1101/2022.02.11.479928
Mehdi Zouiouich, Thomas Di Mattia, Arthur Martinet, Julie Eichler, C. Wendling, Nario Tomishige, Erwan Grandgirard, Nicolas Fuggetta, C. Ramain, Giulia Mizzon, Calvin Dumesnil, Maxime Carpentier, B. Reina-San-Martin, C. Mathelin, Y. Schwab, A. Thiam, Toshihide Kobayashi, G. Drin, C. Tomasetto, F. Alpy
Membrane contact sites between organelles are organized by protein bridges. Among the components of these contacts, the VAP family comprises endoplasmic reticulum (ER)-anchored proteins, such as MOSPD2, functioning as major ER-organelle tethers. MOSPD2 distinguishes itself from the other members of the VAP family by the presence of a CRAL-TRIO domain. In this study, we show that MOSPD2 forms ER-LD contacts thanks to its CRAL-TRIO domain. MOSPD2 ensures the attachment of the ER to LDs through a direct protein-membrane interaction involving an amphipathic helix that has an affinity for lipid packing defects present at the surface of LDs. Remarkably, the absence of MOSPD2 markedly disturbs the assembly of lipid droplets. These data show that MOSPD2, in addition to being a general ER receptor for inter-organelle contacts, possesses an additional tethering activity and is specifically implicated in the biology of LDs via its CRAL-TRIO domain.
{"title":"MOSPD2 is an endoplasmic reticulum–lipid droplet tether functioning in LD homeostasis","authors":"Mehdi Zouiouich, Thomas Di Mattia, Arthur Martinet, Julie Eichler, C. Wendling, Nario Tomishige, Erwan Grandgirard, Nicolas Fuggetta, C. Ramain, Giulia Mizzon, Calvin Dumesnil, Maxime Carpentier, B. Reina-San-Martin, C. Mathelin, Y. Schwab, A. Thiam, Toshihide Kobayashi, G. Drin, C. Tomasetto, F. Alpy","doi":"10.1101/2022.02.11.479928","DOIUrl":"https://doi.org/10.1101/2022.02.11.479928","url":null,"abstract":"Membrane contact sites between organelles are organized by protein bridges. Among the components of these contacts, the VAP family comprises endoplasmic reticulum (ER)-anchored proteins, such as MOSPD2, functioning as major ER-organelle tethers. MOSPD2 distinguishes itself from the other members of the VAP family by the presence of a CRAL-TRIO domain. In this study, we show that MOSPD2 forms ER-LD contacts thanks to its CRAL-TRIO domain. MOSPD2 ensures the attachment of the ER to LDs through a direct protein-membrane interaction involving an amphipathic helix that has an affinity for lipid packing defects present at the surface of LDs. Remarkably, the absence of MOSPD2 markedly disturbs the assembly of lipid droplets. These data show that MOSPD2, in addition to being a general ER receptor for inter-organelle contacts, possesses an additional tethering activity and is specifically implicated in the biology of LDs via its CRAL-TRIO domain.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"31 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124927155","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
During tissue morphogenesis, cell shape changes resulting from cell-generated forces often require active regulation of intracellular trafficking. How mechanical stimuli influence intracellular trafficking and how such regulation impacts tissue mechanics are not fully understood. In this study, we identify an actomyosin dependent mechanism involving Rab11- mediated trafficking in regulating apical constriction in the Drosophila embryo. During Drosophila mesoderm invagination, apical actin and Myosin II (actomyosin) contractility induces apical accumulation of Rab11-marked vesicle-like structures (“Rab11 vesicles”) by promoting a directional bias in dynein mediated vesicle transport. At the apical domain, Rab11 vesicles are enriched near the adherens junctions (AJs). The apical accumulation of Rab11 vesicles is essential to prevent fragmented apical AJs, breaks in the supracellular actomyosin network and a reduction in the apical constriction rate. This Rab11 function is separate from its role in promoting apical Myosin II accumulation. These findings suggest a feedback mechanism between actomyosin activity and Rab11-mediated intracellular trafficking that regulates the force generation machinery during tissue folding.
{"title":"Actomyosin activity-dependent apical targeting of Rab11 vesicles reinforces apical constriction","authors":"Wei Chen, Bing He","doi":"10.1083/jcb.202103069","DOIUrl":"https://doi.org/10.1083/jcb.202103069","url":null,"abstract":"During tissue morphogenesis, cell shape changes resulting from cell-generated forces often require active regulation of intracellular trafficking. How mechanical stimuli influence intracellular trafficking and how such regulation impacts tissue mechanics are not fully understood. In this study, we identify an actomyosin dependent mechanism involving Rab11- mediated trafficking in regulating apical constriction in the Drosophila embryo. During Drosophila mesoderm invagination, apical actin and Myosin II (actomyosin) contractility induces apical accumulation of Rab11-marked vesicle-like structures (“Rab11 vesicles”) by promoting a directional bias in dynein mediated vesicle transport. At the apical domain, Rab11 vesicles are enriched near the adherens junctions (AJs). The apical accumulation of Rab11 vesicles is essential to prevent fragmented apical AJs, breaks in the supracellular actomyosin network and a reduction in the apical constriction rate. This Rab11 function is separate from its role in promoting apical Myosin II accumulation. These findings suggest a feedback mechanism between actomyosin activity and Rab11-mediated intracellular trafficking that regulates the force generation machinery during tissue folding.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"69 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131993874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-01-05DOI: 10.1101/2022.01.05.475028
Yohei Kono, S. Adam, K. Reddy, Yixian Zheng, O. Medalia, R. Goldman, H. Kimura, T. Shimi
In mammalian cell nuclei, the nuclear lamina (NL) underlies the nuclear envelope (NE) to maintain nuclear structure. The nuclear lamins, the major structural components of the NL, are involved in the protection against NE rupture induced by mechanical stress. However, the specific role of the lamins in repair of NE ruptures has not been fully determined. Our analyses using immunofluorescence and live-cell imaging revealed that lamin C but not the other lamin isoforms rapidly accumulated at sites of NE rupture induced by laser microirradiation in mouse embryonic fibroblasts. The immunoglobulin-like fold domain and the NLS were required for the recruitment from the nucleoplasm to the rupture sites with the Barrier-to-autointegration factor (BAF). The accumulation of nuclear BAF and cytoplasmic cyclic GMP-AMP synthase (cGAS) at the rupture sites was in part dependent on lamin A/C. These results suggest that nucleoplasmic lamin C, BAF and cGAS concertedly accumulate at sites of NE rupture for repair. Summary Kono et al. show the rapid recruitment of nucleoplasmic lamin C to sites of nuclear envelope rupture with Barrier-to-autointegration factor. Lamin A/C is also involved in nuclear DNA sensing with cytoplasmic cGAS at the ruptured sites.
{"title":"Nucleoplasmic lamin C rapidly accumulates at sites of nuclear envelope rupture with BAF and cGAS","authors":"Yohei Kono, S. Adam, K. Reddy, Yixian Zheng, O. Medalia, R. Goldman, H. Kimura, T. Shimi","doi":"10.1101/2022.01.05.475028","DOIUrl":"https://doi.org/10.1101/2022.01.05.475028","url":null,"abstract":"In mammalian cell nuclei, the nuclear lamina (NL) underlies the nuclear envelope (NE) to maintain nuclear structure. The nuclear lamins, the major structural components of the NL, are involved in the protection against NE rupture induced by mechanical stress. However, the specific role of the lamins in repair of NE ruptures has not been fully determined. Our analyses using immunofluorescence and live-cell imaging revealed that lamin C but not the other lamin isoforms rapidly accumulated at sites of NE rupture induced by laser microirradiation in mouse embryonic fibroblasts. The immunoglobulin-like fold domain and the NLS were required for the recruitment from the nucleoplasm to the rupture sites with the Barrier-to-autointegration factor (BAF). The accumulation of nuclear BAF and cytoplasmic cyclic GMP-AMP synthase (cGAS) at the rupture sites was in part dependent on lamin A/C. These results suggest that nucleoplasmic lamin C, BAF and cGAS concertedly accumulate at sites of NE rupture for repair. Summary Kono et al. show the rapid recruitment of nucleoplasmic lamin C to sites of nuclear envelope rupture with Barrier-to-autointegration factor. Lamin A/C is also involved in nuclear DNA sensing with cytoplasmic cGAS at the ruptured sites.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121764746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-19DOI: 10.1101/2021.12.17.473229
Juan J Pérez-Moreno, Rebecca C. Smith, M. Oliva, C. O’Kane
Neuronal endoplasmic reticulum (ER) appears continuous throughout the cell. Its shape and continuity are influenced by ER-shaping proteins, mutations in which can cause distal axon degeneration in Hereditary Spastic Paraplegia (HSP). We therefore asked how loss of Rtnl1, a Drosophila ortholog of the human HSP gene RTN2 (SPG12), which encodes an ER-shaping protein, affects ER organization and the function of presynaptic terminals. Loss of Rtnl1 depleted ER membrane markers at Drosophila presynaptic motor terminals, and appeared to deplete narrow tubular ER while leaving cisternae largely unaffected, thus suggesting little change in resting Ca2+ storage capacity. Nevertheless, these changes were accompanied by major reductions in activity-evoked Ca2+ fluxes in the cytosol, ER lumen, and mitochondria, as well as reduced evoked and spontaneous neurotransmission. We found that reduced STIM-mediated ER-plasma membrane contacts underlie presynaptic Ca2+ defects in Rtnl1 mutants. Our results show the importance of ER architecture in presynaptic physiology and function which are therefore potential factors in the pathology of HSP.
{"title":"Drosophila SPG12 ortholog, reticulon-like 1, governs presynaptic ER organization and Ca2+ dynamics","authors":"Juan J Pérez-Moreno, Rebecca C. Smith, M. Oliva, C. O’Kane","doi":"10.1101/2021.12.17.473229","DOIUrl":"https://doi.org/10.1101/2021.12.17.473229","url":null,"abstract":"Neuronal endoplasmic reticulum (ER) appears continuous throughout the cell. Its shape and continuity are influenced by ER-shaping proteins, mutations in which can cause distal axon degeneration in Hereditary Spastic Paraplegia (HSP). We therefore asked how loss of Rtnl1, a Drosophila ortholog of the human HSP gene RTN2 (SPG12), which encodes an ER-shaping protein, affects ER organization and the function of presynaptic terminals. Loss of Rtnl1 depleted ER membrane markers at Drosophila presynaptic motor terminals, and appeared to deplete narrow tubular ER while leaving cisternae largely unaffected, thus suggesting little change in resting Ca2+ storage capacity. Nevertheless, these changes were accompanied by major reductions in activity-evoked Ca2+ fluxes in the cytosol, ER lumen, and mitochondria, as well as reduced evoked and spontaneous neurotransmission. We found that reduced STIM-mediated ER-plasma membrane contacts underlie presynaptic Ca2+ defects in Rtnl1 mutants. Our results show the importance of ER architecture in presynaptic physiology and function which are therefore potential factors in the pathology of HSP.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134172769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-06DOI: 10.1101/2021.12.06.471477
Emily D. Duncan, Ke-jun Han, Margaret A. Trout, R. Prekeris
Cell migration is a complex process that involves coordinated changes in membrane transport, actin cytoskeleton dynamics, and extracellular matrix remodeling. Ras-like small monomeric GTPases, such as Rap2, play a key role in regulating actin cytoskeleton dynamics and cell adhesions. However, how Rap2 function, localization, and activation are regulated during cell migration is not fully understood. We previously identified the small GTPase Rab40b as a regulator of breast cancer cell migration. Rab40b contains a Suppressor of Cytokine Signaling (SOCS) box, which facilitates binding to Cullin5, a known E3 Ubiquitin Ligase component responsible for protein ubiquitylation. In this study, we show that the Rab40b/Cullin5 complex ubiquitylates Rap2. Importantly, we demonstrate that ubiquitylation regulates Rap2 activation, as well as recycling of Rap2 from the endolysosomal compartment to the lamellipodia of migrating breast cancer cells. Based on these data, we propose that Rab40b/Cullin5 ubiquitylates and regulates Rap2-dependent actin dynamics at the leading-edge, a process that is required for breast cancer cell migration and invasion. SUMMARY The Rab40b/Cul5 complex is an emerging pro-migratory molecular machine. Duncan et al. identify the small GTPase Rap2 as a substrate of the Rab40b/Cul5 complex. They provide evidence that Rab40b/Cul5 ubiquitylates Rap2 to regulate its localization and activity during breast cancer cell migration, ultimately proposing a model by which Rap2 is targeted to the leading-edge plasma membrane to regulate actin dynamics during cell migration.
{"title":"Ubiquitylation by Rab40b/Cul5 regulates Rap2 localization and activity during cell migration","authors":"Emily D. Duncan, Ke-jun Han, Margaret A. Trout, R. Prekeris","doi":"10.1101/2021.12.06.471477","DOIUrl":"https://doi.org/10.1101/2021.12.06.471477","url":null,"abstract":"Cell migration is a complex process that involves coordinated changes in membrane transport, actin cytoskeleton dynamics, and extracellular matrix remodeling. Ras-like small monomeric GTPases, such as Rap2, play a key role in regulating actin cytoskeleton dynamics and cell adhesions. However, how Rap2 function, localization, and activation are regulated during cell migration is not fully understood. We previously identified the small GTPase Rab40b as a regulator of breast cancer cell migration. Rab40b contains a Suppressor of Cytokine Signaling (SOCS) box, which facilitates binding to Cullin5, a known E3 Ubiquitin Ligase component responsible for protein ubiquitylation. In this study, we show that the Rab40b/Cullin5 complex ubiquitylates Rap2. Importantly, we demonstrate that ubiquitylation regulates Rap2 activation, as well as recycling of Rap2 from the endolysosomal compartment to the lamellipodia of migrating breast cancer cells. Based on these data, we propose that Rab40b/Cullin5 ubiquitylates and regulates Rap2-dependent actin dynamics at the leading-edge, a process that is required for breast cancer cell migration and invasion. SUMMARY The Rab40b/Cul5 complex is an emerging pro-migratory molecular machine. Duncan et al. identify the small GTPase Rap2 as a substrate of the Rab40b/Cul5 complex. They provide evidence that Rab40b/Cul5 ubiquitylates Rap2 to regulate its localization and activity during breast cancer cell migration, ultimately proposing a model by which Rap2 is targeted to the leading-edge plasma membrane to regulate actin dynamics during cell migration.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"132 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133673479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Zappa, N. Muniozguren, J. C. Ponce-Rojas, D. Acosta-Alvear
The double-stranded RNA sensor kinase PKR is one of four integrated stress response (ISR) sensor kinases that phosphorylate the alpha subunit of the eukaryotic initiation factor 2 (eIF2α) in response to stress. The current model of PKR activation considers the formation of back-to-back PKR dimers as a prerequisite for signal propagation. Here we show that PKR signaling involves the assembly of dynamic PKR clusters. PKR clustering is driven by ligand binding to PKR’s sensor domain and by front-to-front interfaces between PKR’s kinase domains. PKR clusters are discrete, heterogeneous, autonomous coalescences that share some protein components with processing bodies. Strikingly, eIF2α is not recruited to PKR clusters, and PKR cluster disruption enhances eIF2α phosphorylation. Together, these results support a model in which PKR clustering buffers downstream signaling, which may enable proofreading the ISR.
{"title":"Signaling by the integrated stress response kinase PKR is fine-tuned by dynamic clustering","authors":"F. Zappa, N. Muniozguren, J. C. Ponce-Rojas, D. Acosta-Alvear","doi":"10.1083/jcb.202111100","DOIUrl":"https://doi.org/10.1083/jcb.202111100","url":null,"abstract":"The double-stranded RNA sensor kinase PKR is one of four integrated stress response (ISR) sensor kinases that phosphorylate the alpha subunit of the eukaryotic initiation factor 2 (eIF2α) in response to stress. The current model of PKR activation considers the formation of back-to-back PKR dimers as a prerequisite for signal propagation. Here we show that PKR signaling involves the assembly of dynamic PKR clusters. PKR clustering is driven by ligand binding to PKR’s sensor domain and by front-to-front interfaces between PKR’s kinase domains. PKR clusters are discrete, heterogeneous, autonomous coalescences that share some protein components with processing bodies. Strikingly, eIF2α is not recruited to PKR clusters, and PKR cluster disruption enhances eIF2α phosphorylation. Together, these results support a model in which PKR clustering buffers downstream signaling, which may enable proofreading the ISR.","PeriodicalId":343306,"journal":{"name":"The Journal of Cell Biology","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128321636","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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