ABSTRACT
Proteins that enter the secretory pathway are transported from their place of synthesis in the Endoplasmic Reticulum (ER) to the Golgi apparatus by COPII coated carriers. The components of the COPII transport machinery have been well characterized, but the network of proteins that regulate these components have remained largely elusive. The discovery of such regulatory proteins is crucial for understanding how cells integrate intracellular and extracellular information to fine-tune membrane traffic in the secretory pathway. A key group of proteins that plays a central role in the regulation of membrane traffic is associated with the cytoskeleton. Using high throughput microscopy of the well-established VSVG transport from the ER to the plasma membrane, we comprehensively screened 378 cytoskeleton-associated proteins for their functional interaction with the COPII components SEC23A and SEC23B using a double knockdown approach. Ranking of the transport effectors identified 20 cytoskeleton-associated proteins as the strongest functional interactors of SEC23, most of them not previously associated with the secretory pathway. Six of the functional SEC23B interactors (FERMT2, NGEF, MACF1, MAPK8IP2, PIK3CA, ROCK1), which were previously functionally related to cell adhesion, strongly inhibited cargo export from the ER. Surprisingly, knockdown of these SEC23B interactors resulted in the downregulation of SEC23A, a SEC23 paralogue that has been implicated in the secretion of extracellular matrix components. Furthermore, SEC23A downregulation could also be achieved by plating cells on extracellular matrix (ECM) and was dependent on focal adhesions function. Altogether, our results identify a network of cytoskeleton-associated proteins connecting ECM related signalling with the gene expression of the COPII secretory machinery.
Competing Interest Statement
The authors have declared no competing interest.
