 In response to Sema3A signaling cascade, CRMPs which exist as a heterotetramer in the cytosol bind to the cytosolic domain of PlexA and its conformation changes.Further, CRMPs are phosphorylated by Cdk5, GSK3β, and Fes, a tyrosine protein kinase.Especially, phosphorylation of CRMP-1 and CRMP-2 are essential for Sema3A-regulated axonal guidance.