The mammalian NEKs are a highly conserved family of protein kinases that have been primarily implicated in molecular functions linked to cell division and ciliogenesis. We have shown that two C. elegans NEK family members, NEKL-2/NEK8/9 and NEKL-3/NEK6/7, control clathrin mediated endocytosis in the major epidermis of C. elegans. Specifically, NEKL-2 and NEKL-3 (NEKLs) are required for the internalization of cargo, such as the lipoprotein receptor LRP-1, at the apical plasma membrane. Our data indicate that NEKLs control endocytosis at least in part by promoting the uncoating of newly internalized clathrin-coated vesicles. Loss of NEKL functions lead to a failure of worms to complete molting, resulting in arrested larval development. Attesting to their conserved functions, the mammalian orthologs of NEKL-3, NEK6 and NEK7, are able to rescue molting and trafficking defects when expressed in
nekl-3 deficient worms. To further broaden our understanding of NEK family functions in intracellular trafficking we have analyzed the effects of NEKL depletion on additional cargos and vesicular compartments. We find that in addition to functioning in clathrin mediated endocytosis at the apical membrane, NEKLs also promote clathrin dependent and independent endocytosis at the basolateral membrane in the worm epidermis. Specifically, we find that the class I TGF-beta receptor, SMA-6, and the class II TGF-beta receptor, DAF-4, accumulate to high levels on basolateral membranes following NEKL-3 depletion. In addition, our observations suggest that NEKLs may affect trafficking steps downstream of endocytosis, consistent with the localization of NEKL-3 and NEKL-2 to early and late endosomal compartments, respectively. To extend our findings from worms to mammals, we have begun to characterize the potential trafficking functions of mammalian NEK6 and NEK7 kinases in cell culture. Current data indicate that NEK7 promotes clathrin mediated endocytosis including the observed reduced uptake of the transferrin receptor following NEK7 siRNA depletion. In addition, NEK7 may affect several other trafficking processes in cells including endosomal recycling, membrane fission, and caveoli-dependent endocytosis. Collectively, our studies further support a largely overlooked but conserved function for NEK family kinases in intracellular trafficking.