Ankyrin binding mediates L1CAM interactions with static components of the cytoskeleton and inhibits retrograde movement of L1CAM on the cell surface

Abstract

The function of adhesion receptors in both cell adhesion and migration depends critically on interactions with the cytoskeleton. During cell adhesion, cytoskeletal interactions stabilize receptors to strengthen adhesive contacts. In contrast, during cell migration, adhesion proteins are believed to interact with dynamic components of the cytoskeleton, permitting the transmission of traction forces through the receptor to the extracellular environment. The L1 cell adhesion molecule (L1CAM), a member of the Ig superfamily, plays a crucial role in both the migration of neuronal growth cones and the static adhesion between neighboring axons. To understand the basis of L1CAM function in adhesion and migration, we quantified directly the diffusion characteristics of L1CAM on the upper surface of ND-7 neuroblastoma hybrid cells as an indication of receptor–cytoskeleton interactions. We find that cell surface L1CAM engages in diffusion, retrograde movement, and stationary behavior, consistent with interactions between L1CAM and two populations of cytoskeleton proteins. We provide evidence that the cytoskeletal adaptor protein ankyrin mediates stationary behavior while inhibiting the actin-dependent retrograde movement of L1CAM. Moreover, inhibitors of L1CAM–ankyrin interactions promote L1CAM-mediated axon growth. Together, these results suggest that ankyrin binding plays a crucial role in the anti-coordinate regulation of L1CAM-mediated adhesion and migration.

Hepatocyte Growth Factor-induced Ectodomain Shedding of Cell Adhesion Molecule L1

“…A second mutant with an exchange of tyrosine 1229 to histidine (L1YH) was generated. This mutation known from the MASA syndrome abolishes the tyrosine phosphorylation-mediated intracellular binding of L1 to ankyrin (32) and enhances lateral motility of L1 (23).…”

“…Ankyrin links L1 via spectrin to the actin cytoskeleton (21). To elucidate the role of the actin cytoskeleton in L1 shedding, we treated transfected 293T L1wt cells for 3 h with cytochalasin D at a concentration known to completely suppress F-actin polymerization in the periphery of cells (23). Viability of cells was determined by the trypan blue viability test and was found to be similar in treated and untreated cells (95%).…”

“…This is suggested by the findings that L1-mediated cell adhesion activates the fibroblast growth factor (FGF) receptor (19) and the epidermal growth factor (EGF) receptor (20) tyrosine phosphorylation, respectively, the latter an effect which appears to involve L1/EGF receptor trans interactions (20). On the other hand, the cytoplasmic domain of L1 contains several phosphorylation sites and it was shown before that phosphorylation events induced by growth factors regulate the interaction of the L1 family member neurofascin with the ankyrin/actin network and L1 lateral movement (21)(22)(23). We show here that shedding of L1 is a regulated process, triggered by the physiological factor HGF, which is overexpressed in renal carcinomas.…”

Novel role for the Lu/BCAM–spectrin interaction in actin cytoskeleton reorganization

“…Other proteins of the spectrin-based cytoskeleton, like the adapter protein ankyrin G, can also modulate adhesion molecules' functions including cell adhesion, migration and membrane distribution. The membrane expression of L1CAM, involved in the migration of neuronal growth cones and the static adhesion between adjacent axons, is regulated by its interaction with ankyrin G. Inhibition of this interaction led to retrograde movements of L1CAM in the cell membrane and stimulated L1CAM-mediated neurite outgrowth [33].…”

Interplay between adhesion turnover and cytoskeleton dynamics in the control of growth cone migration

“…α-and β-catenin in the case of N-cadherin, 10 ankyrin and ezrin in the case of IgCAMs such as L1. [11][12][13][14] These purely mechanical connections can also be accompanied by signalling events such as Rac-1 activation by N-cadherin liganding 15 and phosphorylation of the L1 intracellular tail that regulates binding to ankyrin. 11,12 When only few molecular bonds are formed, e.g.…”