CLP-36 PDZ-LIM protein associates with nonmuscle alpha-actinin-1 and alpha-actinin-4.
The PDZ-LIM family of proteins (Enigma/LMP-1, ENH, ZASP/Cypher, RIL, ALP, and CLP-36) has been suggested to act as adapters that direct LIM-binding proteins to the cytoskeleton. Most interactions of PDZ-LIM proteins with the cytoskeleton have been identified in striated muscle, where several PDZ-LIM proteins are predominantly expressed. By contrast, CLP-36 mRNA is expressed in several nonmuscle tissues, and here we demonstrate high expression of CLP-36 in epithelial cells by in situ hybridization analysis. Our subcellular localization studies indicate that in nonmuscle cells, CLP-36 protein localizes to actin stress fibers. This localization is mediated via the PDZ domain of CLP-36 that associates with the spectrin-like repeats of alpha-actinin. Interestingly, immunoprecipitation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis indicate that both nonmuscle alpha-actinin-1 and alpha-actinin-4 form complexes with CLP-36. The high expression of alpha-actinin-4 in the colon, together with these results, suggests a specific function for the alpha-actinin-4-CLP-36 complex in the colonic epithelium. More generally, results presented here demonstrate that the association of PDZ-LIM proteins with the cytoskeleton extends to the actin stress fibers of nonmuscle cells.
Vallenius
T
T
Haartman Institute & Biocentrum Helsinki, University of Helsinki, 00014 Helsinki, Finland.
Luukko
K
K
Mäkelä
T P
TP
D000185:Actinin / Q000737:chemistry*; D000818:Animals; D019556:COS Cells; D003599:Cytoskeleton / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000737:chemistry; D018398:Homeodomain Proteins / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry*; D060588:LIM Domain Proteins; D051379:Mice; D008808:Mice, Inbred CBA; D008840:Microfilament Proteins; D011817:Rabbits
C491752:Actn4 protein, mouse; C491751:Actn4 protein, rat; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; D008840:Microfilament Proteins; C486247:PDLIM4 protein, human; C097168:Pdlim1 protein, rat; C486248:Pdlim4 protein, mouse; D000185:Actinin