Functional interplay between ganglioside GM 1 and cross‐linking galectin‐1 induces axon‐like neuritogenesis via integrin‐based signaling and TRPC 5‐dependent Ca 2+ influx

Axon‐like neuritogenesis in neuroblastoma ( NG 108‐15) cells and primary cerebellar granular neurons is furthered by the presence of ganglioside GM 1. We describe here that galectin‐1 (Gal‐1), a homobivalent endogenous lectin, is an effector by cross‐linking the ganglioside and its associated glycoprotein α 5 β 1 ‐integrin. The thereby triggered signaling cascade involves autophosphorylation of focal adhesion kinase and activation of phospholipase Cγ and phosphoinositide‐3 kinase. This leads to a transient increase in the intracellular Ca 2+ concentration by opening of TRPC 5 channels, which belong to the signal transduction‐gated cation channels. Controls with GM 1‐defective cells ( NG ‐ CR 72 and neurons from ganglio‐series KO mice) were retarded in axonal growth, underscoring the relevance of GM 1 as functional counterreceptor for Gal‐1. The lectin's presence was detected in the NG 108‐15 cells, suggesting an autocrine mechanism of action, and in astrocytes in situ . Gal‐1, as cross‐linking lectin, can thus translate metabolic conversion of ganglioside GD 1a to GM 1 by neuraminidase action into axon growth.Galectin‐1 (Gal‐1) was shown an effector of axonogenesis in cerebellar granule neurons (CGNs) and NG108‐15 cells by cross‐linking GM1 ganglioside and its associated glycoprotein α 5 β 1 ‐integrin. The resulting signaling led to a transient increase in intracellular Ca 2+ by opening TRPC5 channels. CGNs deficient in GM1 showed retarded axonogenesis, underscoring the relevance of GM1 as functional counterreceptor for Gal‐1 in this process. This Gal‐1/GM1‐induced signaling was manifest only at the earliest, initiating stage of axon development.