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. Author manuscript; available in PMC: 2009 Apr 1.
Published in final edited form as: Mol Cell Neurosci. 2008 Jan 17;37(4):781–793. doi: 10.1016/j.mcn.2008.01.006

Figure 8. Model for the mechanism of action of the shed NCAM extracellular domain in interneuronal development.

Figure 8

Excess soluble NCAM-EC is depicted to interact with neuronal NCAM to inhibit NCAM-NCAM homophilic binding and heterophilic interactions with receptors such as the FGF receptor (FGFR) (Meiri 1998; Kiselyov 2003; Kiselyov 2005) or receptor protein tyrosine phosphatase alpha (RPTPα, (Bodrikov 2005)), thereby decreasing interneuron arborization to result in fewer perisomatic synapses. Alternatively, in other cell types where metalloprotease-induced soluble NCAM-EC promotes neurite growth (Meiri 1998; Hubschmann 2005; Kalus 2006), transgenic NCAM-EC might bind and inhibit this activity. In normal development, ERK MAP kinase, triggered by an external stimulus, activates an ADAM family protease to cleave NCAM and release NCAM-EC. This serves to limit interneuron branching promoted by NCAM homophilic or heterophilic binding.