Abstract
Coordinated AP-1 and clathrin coat assembly mediate secretory sorting on the trans-Golgi network (TGN) during conventional secretion. Here we found that SMAP-1/SMAPs deficiency caused the apical protein ERM-1 to accumulate on the basolateral side of the TGN. In contrast, the basolateral protein SLCF-1 appeared abnormally on the apical membrane. SMAP-1 colocalized with AP-1 on the TGN. The integrity of AP-1 is required for the subcellular presence of SMAP-1. Moreover, we found that the loss of SMAP-1 reduced clathrin-positive structures in the cytosol, suggesting that SMAP-1 has a regulatory role in clathrin assembly on the TGN. Functional experiments showed that overexpressing clathrin effectively alleviated exocytic defects due to the lack of SMAP-1, corroborating the role of SMAP-1 in promoting the assembly of clathrin on the TGN. Together, our results suggested that the AP-1 complex regulates the TGN localization of SMAP-1, promoting clathrin assembly to ensure polarized conventional secretion in C. elegans intestinal epithelia.
Highlights
In the conventional secretion pathway, cargo proteins traverse endoplasmic reticulum (ER)-Golgi and reach the plasma membrane via transport vesicles (Mellman and Warren, 2000; Rabouille, 2017; Dimou and Nickel, 2018)
We found that SMAP-1 deficiency led to a loss of trans-Golgi network (TGN) localization of clathrin
A recent study showed that SMAP2 facilitates clathrin assembly protein (CALM) mediated formation of clathrin-coated carriers on the TGN, promoting acrosome formation (Funaki et al, 2013)
Summary
In the conventional secretion pathway, cargo proteins traverse ER-Golgi and reach the plasma membrane via transport vesicles (Mellman and Warren, 2000; Rabouille, 2017; Dimou and Nickel, 2018). There are apical and basolateral membrane domains in epithelial cells, which leads to additional complexity of cargo sorting (Yeaman et al, 1999; Ang et al, 2003; Sato et al, 2007; Nakajo et al, 2016). Delicate sorting machinery is employed to package the cargo proteins into specific vesicles and deliver them to various downstream destinations. TGN missorting can lead to inappropriate targeting of cargo proteins and cell polarity defects (Guo et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
