Limits...
Sec16 influences transitional ER sites by regulating rather than organizing COPII.

Bharucha N, Liu Y, Papanikou E, McMahon C, Esaki M, Jeffrey PD, Hughson FM, Glick BS - Mol. Biol. Cell (2013)

Bottom Line: An upstream conserved region (UCR) localizes Sec16 to tER sites.We propose that Sec16 does not in fact organize COPII.Instead, regulation of COPII turnover can account for the influence of Sec16 on tER sites.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637 Department of Molecular Biology, Princeton University, Princeton, NJ 08544.

ABSTRACT
During the budding of coat protein complex II (COPII) vesicles from transitional endoplasmic reticulum (tER) sites, Sec16 has been proposed to play two distinct roles: negatively regulating COPII turnover and organizing COPII assembly at tER sites. We tested these ideas using the yeast Pichia pastoris. Redistribution of Sec16 to the cytosol accelerates tER dynamics, supporting a negative regulatory role for Sec16. To evaluate a possible COPII organization role, we dissected the functional regions of Sec16. The central conserved domain, which had been implicated in coordinating COPII assembly, is actually dispensable for normal tER structure. An upstream conserved region (UCR) localizes Sec16 to tER sites. The UCR binds COPII components, and removal of COPII from tER sites also removes Sec16, indicating that COPII recruits Sec16 rather than the other way around. We propose that Sec16 does not in fact organize COPII. Instead, regulation of COPII turnover can account for the influence of Sec16 on tER sites.

Show MeSH

Related in: MedlinePlus

Models for Sec16 function. (A) Diagram summarizing the conserved regions of P. pastoris Sec16 and their inferred functions. See the text for details. (B) Speculative diagram of a cross section through a nascent COPII vesicle. Sar1 has largely dissociated from the interior of the coat lattice due to Sec23- and Sec31-catalyzed GTP hydrolysis. However, a ring of Sar1-GTP is maintained at the edge of the lattice because Sec16 binds to the newly assembled COPII coat subunits and slows Sar1 GTPase activity. Sec16 also recruits Sec12 to the vicinity of the budding vesicle, leading to enhanced local production of Sar1-GTP. See the text for further details.
© Copyright Policy - creative-commons
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3814151&req=5

Figure 9: Models for Sec16 function. (A) Diagram summarizing the conserved regions of P. pastoris Sec16 and their inferred functions. See the text for details. (B) Speculative diagram of a cross section through a nascent COPII vesicle. Sar1 has largely dissociated from the interior of the coat lattice due to Sec23- and Sec31-catalyzed GTP hydrolysis. However, a ring of Sar1-GTP is maintained at the edge of the lattice because Sec16 binds to the newly assembled COPII coat subunits and slows Sar1 GTPase activity. Sec16 also recruits Sec12 to the vicinity of the budding vesicle, leading to enhanced local production of Sar1-GTP. See the text for further details.

Mentions: This essential function of Sec16 is apparently mediated by the CTR, which displays sequence conservation between fungi and mammals (Bhattacharyya and Glick, 2007). In our hands, the CTR is the only part of Sec16 that could not be deleted without killing the cells. The CTR has a conserved interaction with Sec23 (Espenshade et al., 1995; Bhattacharyya and Glick, 2007). This interaction was recently shown to prevent Sec31 from stimulating the GTPase-activating activity of Sec23, so the net effect of the Sec16–Sec23 interaction is to stabilize Sar1-GTP in the COPII coat (Kung et al., 2011; Yorimitsu and Sato, 2012). Figure 9A presents an overview of the known interactions and functions of the various regions of Sec16.


Sec16 influences transitional ER sites by regulating rather than organizing COPII.

Bharucha N, Liu Y, Papanikou E, McMahon C, Esaki M, Jeffrey PD, Hughson FM, Glick BS - Mol. Biol. Cell (2013)

Models for Sec16 function. (A) Diagram summarizing the conserved regions of P. pastoris Sec16 and their inferred functions. See the text for details. (B) Speculative diagram of a cross section through a nascent COPII vesicle. Sar1 has largely dissociated from the interior of the coat lattice due to Sec23- and Sec31-catalyzed GTP hydrolysis. However, a ring of Sar1-GTP is maintained at the edge of the lattice because Sec16 binds to the newly assembled COPII coat subunits and slows Sar1 GTPase activity. Sec16 also recruits Sec12 to the vicinity of the budding vesicle, leading to enhanced local production of Sar1-GTP. See the text for further details.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3814151&req=5

Figure 9: Models for Sec16 function. (A) Diagram summarizing the conserved regions of P. pastoris Sec16 and their inferred functions. See the text for details. (B) Speculative diagram of a cross section through a nascent COPII vesicle. Sar1 has largely dissociated from the interior of the coat lattice due to Sec23- and Sec31-catalyzed GTP hydrolysis. However, a ring of Sar1-GTP is maintained at the edge of the lattice because Sec16 binds to the newly assembled COPII coat subunits and slows Sar1 GTPase activity. Sec16 also recruits Sec12 to the vicinity of the budding vesicle, leading to enhanced local production of Sar1-GTP. See the text for further details.
Mentions: This essential function of Sec16 is apparently mediated by the CTR, which displays sequence conservation between fungi and mammals (Bhattacharyya and Glick, 2007). In our hands, the CTR is the only part of Sec16 that could not be deleted without killing the cells. The CTR has a conserved interaction with Sec23 (Espenshade et al., 1995; Bhattacharyya and Glick, 2007). This interaction was recently shown to prevent Sec31 from stimulating the GTPase-activating activity of Sec23, so the net effect of the Sec16–Sec23 interaction is to stabilize Sar1-GTP in the COPII coat (Kung et al., 2011; Yorimitsu and Sato, 2012). Figure 9A presents an overview of the known interactions and functions of the various regions of Sec16.

Bottom Line: An upstream conserved region (UCR) localizes Sec16 to tER sites.We propose that Sec16 does not in fact organize COPII.Instead, regulation of COPII turnover can account for the influence of Sec16 on tER sites.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637 Department of Molecular Biology, Princeton University, Princeton, NJ 08544.

ABSTRACT
During the budding of coat protein complex II (COPII) vesicles from transitional endoplasmic reticulum (tER) sites, Sec16 has been proposed to play two distinct roles: negatively regulating COPII turnover and organizing COPII assembly at tER sites. We tested these ideas using the yeast Pichia pastoris. Redistribution of Sec16 to the cytosol accelerates tER dynamics, supporting a negative regulatory role for Sec16. To evaluate a possible COPII organization role, we dissected the functional regions of Sec16. The central conserved domain, which had been implicated in coordinating COPII assembly, is actually dispensable for normal tER structure. An upstream conserved region (UCR) localizes Sec16 to tER sites. The UCR binds COPII components, and removal of COPII from tER sites also removes Sec16, indicating that COPII recruits Sec16 rather than the other way around. We propose that Sec16 does not in fact organize COPII. Instead, regulation of COPII turnover can account for the influence of Sec16 on tER sites.

Show MeSH
Related in: MedlinePlus