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SUMMARY:Inspecting the early secretory pathway with whole-cell\, volumetri
 c FIB-SEM in fed and starved cells - Professor Jennifer Lippincott-Schwart
 z\, Howard Hughes Medical Institute\, Janelia Research Campus\, Ashburn\, 
 VA
DTSTART:20211118T140000Z
DTEND:20211118T150000Z
UID:TALK161104@talks.cam.ac.uk
CONTACT:Caroline Newnham
DESCRIPTION:Inside of a cell\, snaking membranes comprising the ER synthes
 ize up to 30% of the proteins encoded for by the genome. Many of these new
 ly minted proteins only function after being exported from the ER to other
  cellular destinations. This occurs at sites distributed across the ER cal
 led ER exit sites (ERESs). In this talk\, I present work characterizing ER
 ESs and the secretory pathway using high resolution imaging technologies\,
  including whole-cell volumetric FIB-SEM. Rather than vesicles alone\, we 
 find that the ER spawns an elaborate\, interwoven tubular network of conti
 guous lipid bilayers (ER exit site) for protein export. This receptacle is
  capable of extending microns along microtubules while still connected to 
 the ER by a thin neck. COPII localizes to this neck region and dynamically
  regulates cargo entry from the ER\, while COPI acts more distally\, escor
 ting the detached\, accelerating tubular entity on its way to joining the 
 Golgi apparatus through microtubule-directed movement. Examining starved c
 ells\, where the secretory transport activity of ERESs switches to an auto
 phagic role\, we observe entire ERESs becoming encapsulated into lysosomes
  by FIB-SEM. We show this is mediated by ubiquitinated Sec31 and other mac
 hinery remodeling ERESs\, triggering its engulfment by nearby lysosomes th
 rough an ESCRT-III dependent mechanism. This process could facilitate surv
 ival under starvation by facilitating bulk turnover of secretory pathway c
 omponents.
LOCATION:Zoom meeting
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