The Axonal Membrane Protein PRG2 Inhibits PTEN and Directs Growth to Branches.

In developing neurons, phosphoinositide 3-kinases (PI3Ks) control axon growth and branching by positively regulating PI3K/PI(3,4,5)P 3 , but how neurons are able to generate sufficient PI(3,4,5)P 3 in the presence of high levels of the antagonizing phosphatase PTEN is difficult to reconcile. We find that normal axon morphogenesis involves homeostasis of elongation and branch growth controlled by accumulation of PI(3,4,5)P 3 through PTEN inhibition. We identify a plasma membrane-localized protein-protein interaction of PTEN with plasticity-related gene 2 (PRG2). PRG2 stabilizes membrane PI(3,4,5)P 3 by inhibiting PTEN and localizes in nanoclusters along axon membranes when neurons initiate their complex branching behavior. We demonstrate that PRG2 is both sufficient and necessary to account for the ability of neurons to generate axon filopodia and branches in dependence on PI3K/PI(3,4,5)P 3 and PTEN. Our data indicate that PRG2 is part of a neuronal growth program that induces collateral branch growth in axons by conferring local inhibition of PTEN. • Neuronal axon growth and branching is globally regulated by PI3K/PTEN signaling • PRG2 inhibits PTEN and stabilizes PIP3 and F-actin • PRG2 localizes to nanoclusters on the axonal membrane and coincides with branching • PRG2 promotes axonal filopodia and branching dependent on PI3K/PTEN PTEN globally suppresses growth in multiple cell types and inhibits neuronal axon growth and branching. Brosig et al. describe a mechanism for developing neurons to inhibit PTEN function by upregulating PRG2 in the axon. Although the overall growth capacity of neurons remains constant, PRG2 redirects growth to axon branches. [ABSTRACT FROM AUTHOR]