Essential role of type Iα phosphatidylinositol 4-phosphate 5-kinase in neurite remodeling

Rapid neurite remodeling is fundamental to nervous system development and plasticity 11] and is regulated by Rho family GTPases that signal f-actin reorganization in response to various receptor ligands. Neuronal N1E-115 cells show dramatic neurite retraction and cell rounding in response to serum factors such as lysophosphatidic acid (LPA), sphingosine-1 phosphate (SIP), and thrombin, due to activation of the RhoA-Rho kinase pathway [2]. Type I phosphatidylinositol 4-phosphate 5-kinases (PIPkinase), which regulate cellular levels of PtdIns(4,5)P2 [3], have been suggested as targets of the RhoA-Rho kinase pathway [4, 5] able to modulate cytoskeletal dynamics [6, 7]. Here, we show that the introduction of Type la PIPkinase into N1E-115 cells leads to cell rounding and complete inhibition of neurite outgrowth, perhaps through the dissociation of vinculin and the destabilization of focal adhesions. This occurs independently of RhoA, Rho kinase, and the activation of actomyosin contraction. Strikingly, expression of kinase-dead P1Pkinase promotes the outgrowth of neurites, which fail to retract in response to LPA, SIP, thrombin, or active RhoA. Moreover, neurite retraction in response to an endogenous neuronal guidance cue, Semaphorin3A, was also dependent on Type la P1Pkinase. Our results suggest an essential role for a Type I P1Pkinase during neurite retraction in response to a number of diverse stimuli.