Journal of Biological Chemistry
Volume 284, Issue 43, 23 October 2009, Pages 29437-29445
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Mechanisms of Signal Transduction
Radial Spoke Protein 3 Is a Mammalian Protein Kinase A-anchoring Protein That Binds ERK1/2*

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Initially identified in Chlamydomonas, RSP3 (radial spoke protein 3) is 1 of more than 20 identified radial spoke structural components of motile cilia and is required for axonemal sliding and flagellar motility. The mammalian orthologs for this and other radial spoke proteins, however, remain to be characterized. We found mammalian RSP3 to bind to the MAPK ERK2 through a yeast two-hybrid screen designed to identify interacting proteins that have a higher affinity for the phosphorylated, active form of the protein kinase. Consistent with the screening result, the human homolog, RSPH3, interacts with and is a substrate for ERK1/2. Moreover, RSPH3 is a protein kinase A-anchoring protein (AKAP) that scaffolds the cAMP-dependent protein kinase holoenzyme. The binding of RSPH3 to the regulatory subunits of cAMP-dependent protein kinase, RIIα and RIIβ, is regulated by ERK1/2 activity and phosphorylation. Here we describe an ERK1/2-interacting AKAP and suggest a mechanism by which cAMP-dependent protein kinase-AKAP binding can be modulated by the activity of other enzymes.

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*

This work was supported, in whole or in part, by National Institutes of Health Grant R37 DK34128. This work was also supported by a grant from the THECB Advanced Research Program and Grant I1243 from the Welch Foundation (to M. H. C.).

1

Performed this work in partial fulfillment of the requirements for the Ph.D. degree.