, 2002). Interestingly, L1 ligation causes dephosphorylation of the L1 endocytosis motif and triggers endocytosis (Schaefer et al., 2002), and similarly, exocytosis can be elicited downstream of L1 ligation (Alberts et al., 2003 and Dequidt et al., 2007), pointing to the essential role of signaling in regulated membrane trafficking. Detachment of traction-force-generating adhesion sites at the cell’s rear, or at the nonturning side of the growth

cone, is also essential for cell and growth cone motility (Broussard et al., 2008). Detachment is often accomplished by endocytic removal of adhesion receptors (for example, Bechara et al., 2008, Chao and Kunz, 2009 and Ezratty et al., 2009), which leads to weakening and ultimately disassembly of adhesive contacts. Endocytosis and reinsertion also play important roles in the “gain control” necessary for enabling continued migration up a concentration gradient by continuously MLN0128 purchase adjusting receptor levels to maintain differential sensitivity (Piper et al., 2005). Endocytosis, signaling, and subsequent disassembly of focal adhesions lead to growth cone collapse downstream of Sema3A (Tojima et al., 2011). L1 endocytosis has been shown to

be important to this process. For example, L1 is required for sema3A-mediated growth cone collapse (Castellani et al., 2004), and L1 endocytosis is involved in downregulating the levels of the semaphorin3A coreceptor, ATM/ATR inhibitor review neuropilin (Bechara et al., 2007). The ability of L1 to bind ERM proteins Monoiodotyrosine via its cytoplasmic tail is important in these semaphorin-mediated events (Mintz et al., 2008). The endocytosis of the L1-neuropilin1 complex also leads to local signaling and disassembly of focal adhesions (Bechara et al.,

2008). Recently, several papers have begun to analyze the requirement for endocytosis and endosomes in neuronal migration. The Hoshino lab demonstrated that rab proteins known to be involved in endosomal trafficking and recycling (rab5 and rab11) are important for normal migration (Kawauchi et al., 2010). It is reasonable to assume that the trafficking of many receptors is altered by downregulation of rab5 or rab11, and many receptor systems are probably affected. The authors demonstrated that N-cadherin surface levels were slightly elevated on the surface of migratory neurons expressing less rab5; β1-integrin distribution, on the other hand, was not obviously disturbed. Downregulation of N-cadherin phenocopied the migration defect of rab downregulation and partially rescued the simultaneous downregulation of rab5. Interestingly, expressing too much N-cadherin also caused migration defects. These observations support the model that precise control of surface distribution of N-cadherin and its recycling are important for normal migration (Kawauchi et al., 2010).