Abstract
The ACK family tyrosine kinase SID-3 is involved in the endocytic uptake of double-stranded RNA. Here we identified SID-3 as a previously unappreciated recycling regulator in the Caenorhabditis elegans intestine. The RAB-10 effector EHBP-1 is required for the endosomal localization of SID-3. Accordingly, animals with loss of SID-3 phenocopied the recycling defects observed in ehbp-1 and rab-10 single mutants. Moreover, we detected sequential protein interactions between EHBP-1, SID-3, NCK-1, and DYN-1. In the absence of SID-3, DYN-1 failed to localize at tubular recycling endosomes, and membrane tubules breaking away from endosomes were mostly absent, suggesting that SID-3 acts synergistically with the downstream DYN-1 to promote endosomal tubule fission. In agreement with these observations, overexpression of DYN-1 significantly increased recycling transport in SID-3-deficient cells. Finally, we noticed that loss of RAB-10 or EHBP-1 compromised feeding RNAi efficiency in multiple tissues, implicating basolateral recycling in the transport of RNA silencing signals. Taken together, our study demonstrated that in C. elegans intestinal epithelia, SID-3 acts downstream of EHBP-1 to direct fission of recycling endosomal tubules in concert with NCK-1 and DYN-1.
Highlights
Recycling endosomes receive cargos from sorting endosomes and eventually deliver them to the cell surface [1, 2]
Our study demonstrated that in C. elegans intestinal epithelia, SID-3 acts downstream of EHBP-1 to direct fission of recycling endosomal tubules in concert with NCK-1 and DYN-1
Recycling endosomes mainly consist of membrane tubules and often undergo membrane fission to generate vesicular carriers, which mediates the delivery of cargo proteins back to the plasma membrane
Summary
Recycling endosomes receive cargos from sorting endosomes and eventually deliver them to the cell surface [1, 2]. Membrane-associated cargos destined for the plasma membrane are concentrated in tubular membrane carriers for proper sorting away from the lumenal content [2,3,4]. Tubular recycling carrier formation involves a variety of regulators including RAB-10/ Rab, EHBP-1/EHBP1, RME-1/EHD1, the actin cytoskeleton, and the exocyst [5,6,7,8,9]. In the C. elegans intestine, RAB-10 functions in sorting endosomes and coordinates basolateral recycling transport upstream of RME-1 [10, 11]. A recent study in C. elegans further showed that the EHBP-1 calponin homology (CH) domain preferentially associates with F-actin, and assists the tubulation of recycling endosomes [5]
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