Phosphorylation of Profilin by ROCK1 Regulates Polyglutamine Aggregation

Abstract

Y-27632, an inhibitor of the Rho-associated kinase ROCK, is a therapeutic lead for Huntington disease (HD). The downstream targets that mediate its inhibitory effects on huntingtin (Htt) aggregation and toxicity are unknown. We have identified profilin, a small actin-binding factor that also interacts with Htt, as being a direct target of the ROCK1 isoform. The overexpression of profilin reduces the aggregation of polyglutamine-expanded Htt and androgen receptor (AR) peptides. This requires profilin's G-actin binding activity and its direct interaction with Htt, which are both inhibited by the ROCK1-mediated phosphorylation of profilin at Ser-137. Y-27632 blocks the phosphorylation of profilin in HEK293 cells and primary neurons, which maintains profilin in an active state. The knockdown of profilin blocks the inhibitory effect of Y-27632 on both AR and Htt aggregation. A signaling pathway from ROCK1 to profilin thus controls polyglutamine protein aggregation and is targeted by a promising therapeutic lead for HD.

ACKNOWLEDGMENTS

We thank Paul Muchowski for generously providing the pGEX-Htt exon 1 (Q25 or Q53) constructs, Shuh Narumiya for pCAG-ROCK1 (wt or KDIA) plasmids, Thomas Leung for pXJ40-ROCK2, Robert Edwards for the pCAGGS vector, and Donald C. Lo for the gWIZ blank vector. We also thank Venu Nemani and Ken Nakamura (in the laboratory of Robert Edwards) for kindly providing the rat brain tissues and Mei Li for helping with the dissections.

This study was supported by the Sandler Family Supporting Foundation (M.I.D.), the Taube Family Foundation Program in Huntington's Disease Research (M.I.D.), the Muscular Dystrophy Association (J.S. and M.I.D.), and the National Institutes of Health (N.A.D., W.J.W., and M.I.D.).