Lipid Raft-dependent Endocytosis of Close Homolog of Adhesion Molecule L1 (CHL1) Promotes Neuritogenesis

Melitta Schachner,Witold Diakowski,Iryna Leshchyns'ka,Jeffrey H. Welch,Vladimir Sytnyk,Hongyuan Yang,Nan Tian

doi:10.1074/jbc.m112.394973

Abstract

CHL1 plays a dual role by either promoting or inhibiting neuritogenesis. We report here that neuritogenesis-promoting ligand-dependent cell surface clustering of CHL1 induces palmitoylation and lipid raft-dependent endocytosis of CHL1. We identify βII spectrin as a binding partner of CHL1, and we show that partial disruption of the complex between CHL1 and βII spectrin accompanies CHL1 endocytosis. Inhibition of the association of CHL1 with lipid rafts by pharmacological disruption of lipid rafts or by mutation of cysteine 1102 within the intracellular domain of CHL1 reduces endocytosis of CHL1. Endocytosis of CHL1 is also reduced by nifedipine, an inhibitor of the L-type voltage-dependent Ca(2+) channels. CHL1-dependent neurite outgrowth is reduced by inhibitors of lipid raft assembly, inhibitors of voltage-dependent Ca(2+) channels, and overexpression of CHL1 with mutated cysteine Cys-1102. Our results suggest that ligand-induced and lipid raft-dependent regulation of CHL1 adhesion via Ca(2+)-dependent remodeling of the CHL1-βII spectrin complex and CHL1 endocytosis are required for CHL1-dependent neurite outgrowth.

Highlights

Cell adhesion molecule close homolog of L1 (CHL1) plays a dual role by either promoting or inhibiting neuritogenesis
Our results suggest that ligandinduced and lipid raft-dependent regulation of CHL1 adhesion via Ca2؉-dependent remodeling of the CHL1-␤II spectrin complex and CHL1 endocytosis are required for CHL1-dependent neurite outgrowth
We show that CHL1 directly associates with ␤II spectrin, and we demonstrate that ligand-induced clustering of CHL1 induces palmitoylation of CHL1 and lipid raft-dependent remodeling of the CHL1-␤II spectrin complex, accompanied by CHL1 endocytosis, which are required for CHL1-dependent neurite outgrowth

Summary

Background

Cell adhesion molecule CHL1 plays a dual role by either promoting or inhibiting neuritogenesis. We report here that neuritogenesis-promoting ligand-dependent cell surface clustering of CHL1 induces palmitoylation and lipid raft-dependent endocytosis of CHL1. The extracellular domain of CHL1 binds to CHL1 molecules on adjacent membranes thereby mediating homophilic interactions [2] It interacts with other adhesion molecules such as integrins [3] and NB-3, a member of the F3/contactin family of neural recognition molecules [4], and cell surface receptors, such as the receptor-type protein-tyrosine phosphatase ␣ [4], semaphorin 3A receptor neuropilin 1 [5], and ephrin A5 receptor [6]. We show that CHL1 directly associates with ␤II spectrin, and we demonstrate that ligand-induced clustering of CHL1 induces palmitoylation of CHL1 and lipid raft-dependent remodeling of the CHL1-␤II spectrin complex, accompanied by CHL1 endocytosis, which are required for CHL1-dependent neurite outgrowth

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION