Nerve growth factor stimulates the interaction of ZIP/p62 with atypical protein kinase C and targets endosomal localization: Evidence for regulation of nerve growth factor-induced differentiation

Atypical protein kinase Cs zeta and lambda/iota play a functional role in the regulation of NGF‐induced differentiation and survival of pheochromocytoma, PC12 cells [Coleman and Wooten, 1994; Wooten et al., 1999]. Here we demonstrate an NGF‐dependent interaction of aPKC with its binding protein, ZIP/p62. Although, ZIP/p62 was not a PKC‐ι substrate, the formation of a ZIP/p62‐aPKC complex in PC12 cells by NGF occurred post activation of PKC‐ι and was regulated by the tyrosine phosphorylation state of aPKC. Furthermore, NGF‐dependent localization of ZIP/p62 was observed within vesicular structures, identified as late endosomes by colocalization with a Rab7 antibody. Both ZIP/p62 as well as PKC‐ι colocalized with Rab7 upon NGF stimulation. Inhibition of the tyrosine phosphorylation state of PKC‐ι did not prevent movement of ZIP/p62 to the endosomal compartment. These observations indicate that the subcellular localization of ZIP/p62 does not depend entirely upon activation of aPKC itself. Of functional importance, transfection of an antisense p62 construct into PC12 cells significantly diminished NGF‐induced neurite outgrowth. Collectively, these findings demonstrate that ZIP/p62 acts as a shuttling protein involved in routing activated aPKC to an endosomal compartment and is required for mediating NGF's biological properties. J. Cell. Biochem. 82:452–466, 2001. © 2001 Wiley‐Liss, Inc.