The homophilic NCAM1:NCAM1 interaction redistributes these molecules and leads to the formation of clusters within lipid rafts. Spectrin, an NCAM1 binding cytoskeletal protein, colocalizes with NCAM1 and codistribute to lipid rafts. Spectrin associates with RPTP-alpha, linking it to the cytoplasmic NCAM1 domain and causing its coredistribution to lipid rafts on NCAM1 clustering. The receptor tyrosine phosphatase RPTP-alpha is an activator of all kinases of the Src family, including Fyn kinase.
The interaction of RPTP-alpha and the SH2 domain of Fyn induces an interaction of Fyn Tyr531 with the D1 domain of RPTP-alpha. This induces dephosphorylation of Tyr531 and activates Fyn.