Control of clathrin-mediated endocytosis by NIMA family kinases

Abstract

Endocytosis, the process by which cells internalize plasma membrane and associated cargo, is regulated extensively by posttranslational modifications. Previous studies suggested the potential involvement of scores of protein kinases in endocytic control, of which only a few have been validated within their native context. Here we show that the conserved NIMA-related kinases NEKL-2/NEK8/9 and NEKL-3/NEK6/7 (the NEKLs) control clathrin-mediated endocytosis in C. elegans. Loss of NEKLs leads to clathrin mislocalization and to a dramatic reduction in clathrin mobility at the apical membrane. Strikingly, reducing the levels of active AP2, the major clathrin adapter complex, rescues nekl mutant defects, whereas increased levels of active AP2 exacerbate nekl defects. Moreover, NEKL inhibition alleviates defects associated with reduced AP2 activity, attesting to the tight link between NEKL and AP2 functions. We also show that NEKLs are required for the clustering and internalization of membrane cargo and that human NEKs rescue defects in nekl mutant worms.

FCHO controls AP2’s initiating role in endocytosis through a PtdIns(4,5)P 2 -dependent switch

“…The unstructured interdomain linkers of FCHO1, FCHO2, and SH3-containing GRB2-like protein 3-interacting protein 1 (sgip1) have been proposed to interact with AP2 ( 11 , 16 , 26 , 42 ). Biolayer interferometry (BLI) under near-physiological conditions, where AP2 core is known to be in its closed cytosolic conformation ( 14 ), showed that the K D values for the direct interactions between AP2core and FCHO2 linker and between AP2core and FCHO1 linker were ~10 μM (Fig.…”

Endocytosis in the adaptation to cellular stress

“…Our lack of understanding of the adaptation of endocytosis under stress conditions goes hand in hand with our limited knowledge about endocytic regulation in other physiological conditions. Even though numerous kinase pathways have been implicated in the regulation of endocytosis [27,117] including some recent additions like the NIMA family kinases in C. elegans [118], how different signal transduction cascades modulate specific endocytic factors and cargo sorting in most cases has remained enigmatic. In addition to phosphorylation, ubiquitination events play a critical role in regulating the uptake of specific cargo proteins.…”

Mutation of NEKL-4/NEK10 and TTLL genes suppress neuronal ciliary degeneration caused by loss of CCPP-1 deglutamylase function

“…C . elegans NEKL-2 and NEKL-3 control clathrin-mediated endocytosis and trafficking in non-ciliated cells [ 69 – 71 ]. NEKL-4 localizes to the periciliary membrane compartment, an active site of endocytosis, a process necessary for regulating ciliary membrane volume, ciliary protein levels, and IFT [ 72 ].…”