The Neural Cell Adhesion Molecule Promotes FGFR-Dependent Phosphorylation and Membrane Targeting of the Exocyst Complex to Induce Exocytosis in Growth Cones

Abstract

The exocyst complex is an essential regulator of polarized exocytosis involved in morphogenesis of neurons. We show that this complex binds to the intracellular domain of the neural cell adhesion molecule (NCAM). NCAM promotes FGF receptor-mediated phosphorylation of two tyrosine residues in the sec8 subunit of the exocyst complex and is required for efficient recruitment of the exocyst complex to growth cones. NCAM at the surface of growth cones induces Ca 2ϩ -dependent vesicle exocytosis, which is blocked by an inhibitor of L-type voltage-dependent Ca 2ϩ channels and tetanus toxin. Preferential exocytosis in growth cones underlying neurite outgrowth is inhibited in NCAM-deficient neurons as well as in neurons transfected with phosphorylation-deficient sec8 and dominant-negative peptides derived from the intracellular domain of NCAM. Thus, we reveal a novel role for a cell adhesion molecule in that it regulates addition of the new membrane to the cell surface of growth cones in developing neurons.

At the Intersection of the Pathways for Exocytosis and Autophagy

“…This has been shown in MSCK cells (Oztan et al, 2007;Zhang et al, 2004), and in Drosophila photoreceptor and sensory neuron cells (Wu et al, 2005). Rab11 is important for the anterograde trafficking of; numerous membrane receptors (Chernyshova et al, 2011), the epithelial sodium channel complex of the cortical collecting duct of the kidneys (Butterworth et al, 2012), and DE-Cadherin in polarised cells (Langevin et al, 2005;Wu et al, 2005;Zhang et al, 2004), as well as the calcium dependent exocytosis of growth hormones (Ren et al, 1998;Takaya et al, 2007). A number of intracellular pathogens, such as Porphyromonas gingivalis, influenza A and HIV, have been reported to hi-jack Rab11 dependent anterograde trafficking as a means of escape from host cells (Kadiu & Gendelman, 2011;Momose et al, 2011;Takeuchi et al, 2011).…”

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

“…Neuronal Cultures-Hippocampal and cortical neurons were prepared from 1-to 3-day-old C57BL/6J mice and maintained for 24 h in Neurobasal A medium supplemented with 2% B-27 and GlutaMAX (Invitrogen) and FGF-2 (2 ng/ml, R&D Systems, Minneapolis, MN) on glass coverslips coated with poly-D-lysine (100 g/ml) (21).…”

RhoGTPase-binding proteins, the exocyst complex and polarized vesicle trafficking

“…30 Within the exocyst members, Sec5 and Exo84 are specific interaction partners of Ral, 27 also present in growing axon terminals. 31 As opposed to Rho and Ral GTPases that regulate exocyst function on target membranes, the Rab family of small GTPases contributes to the specificity of polarized traffic by residing on vesicles arriving at the target membrane.…”