Cilia and mitogen‐activated protein kinase signaling

Abstract

Our lab identified mouse Radial Spoke Protein 3 (RSP3) through a yeast two‐hybrid screen designed to identify interactors that have a higher affinity for the phosphorylated, active form of ERK2 (pERK2). RSP3 is a structural component of motile cilia and an A‐Kinase Anchoring Protein (AKAP) for cAMP‐dependent Protein Kinase (PKA). To confirm our finding, I showed that the human homolog, RSP3H, co‐immunoprecipitates with ERK2 in overexpression studies. Furthermore, I demonstrated, through immunoprecipitation kinase assays, that RSP3H is phosphorylated by pERK2. Additionally, I showed through RT‐PCR that an mRNA transcript of RSP3H is present in HEK293 and HeLa cells, neither of which are thought to contain motile cilia. I also performed immunofluorescence studies on overexpressed RSP3H, and discovered that not only does it localize to cilia‐like structures but also may induce the formation of multiple cilia‐like projections from the cell, thus functioning as a regulator of ciliogenesis. RSP3H may serve to localize ERK1/2 to cilia and function as a point of convergence of cAMP‐dependent and PKA‐mediated action upon ERK1/2 downstream signaling.