Human CLP36, a PDZ-domain and LIM-domain protein, binds to α-actinin-1 and associates with actin filaments and stress fibers in activated platelets and endothelial cells

Abstract

A 38-kd protein that associates with F-actin structures in activated platelets and endothelial cells was purified, cloned, and characterized. The protein contains an N-terminal PDZ motif, a large intervening sequence, and a C-terminal LIM domain and was identified as the human homolog of rat CLP36. The study showed that CLP36 associates with actin filaments and stress fibers that are formed during shape change and spreading of platelets and during migration and contraction of endothelial cells. CLP36 binds to α-actinin-1 as shown by coimmunoprecipitation, pull-down experiments, yeast 2-hybrid analysis, and blot overlay assays and colocalizes with α-actinin-1 along endothelial actin stress fibers. In contrast to α-actinin-1, CLP36 was absent from focal adhesions in both activated platelets and endothelial cells. The N-terminal part of CLP36 containing the PDZ domain and the intervening region, but not the LIM domain, targeted enhanced green fluorescent protein fusion proteins to stress fibers in endothelial cells. Yeast 2-hybrid analysis demonstrated that the intervening sequence, but not the PDZ or the LIM domain of CLP36, binds to the spectrinlike repeats 2 and 3 of α-actinin-1. The study further shows that CLP36 binds to α-actinin in resting platelets and translocates as a CLP36/α-actinin complex to the newly formed actin cytoskeleton in activated platelets. The results indicate that CLP36 binds via α-actinin-1 to actin filaments and stress fibers in activated human platelets and endothelial cells. The study suggests that CLP36 may direct α-actinin-1 to specific actin structures and at this position might modulate the function of α-actinin-1.

RETRACTED: STK35 Gene Therapy Attenuates Endothelial Dysfunction and Improves Cardiac Function in Diabetes

“…STK35 is a component of chromatin remodeling complexes ( 12 ) and, therefore, might directly influence the core transcription machinery and gene expression ( 13 , 14 ). STK35 regulates multiple cellular functions such as cell migration, proliferation, survival, and angiogenesis ( 8 , 15 , 16 ). Moreover, the levels of STK35 were elevated in human colorectal cancer tissues ( 17 ) and altered in a rodent model of Parkinson's disease ( 18 ).…”

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Cysteine-rich protein 1 (CRP1) regulates actin filament bundling

“…Four and a half LIM domain protein 3 (FHL3) has been demonstrated to disrupt actin stress fibers in C2C12 myoblasts presumably by binding to actin filaments and inhibiting α-actinin bundling [ 6 ]. In addition, ENH [ 7 ], ALP [ 8 ], Cypher [ 9 ], CLIM1 [ 10 ], CLP-36 [ 11 , 12 ], zyxin [ 13 ], and the cysteine-rich protein (CRP) family [ 14 , 15 ] have also been demonstrated to interact with α-actinin, although it is not clear if these proteins influence α-actinin function.…”

Susceptibility to glaucoma: differential comparison of the astrocyte transcriptome from glaucomatous African American and Caucasian American donors

“…The Nck1 SH2/SH3 adaptor couples phosphotyrosine signals to the actin cytoskeleton and receptor signaling to the regulatory machinery of the cytoskeleton [ 42 ]. The enigma family member PDLIM1 was upregulated in AAG astrocytes (Table 3 ) and functions by allowing interactions among cytoskeletal proteins through PDZ and amino LIM domains [ 43 , 44 ]. Downregulation of other actin binding proteins such as PLEC1 (Table 3 ) may alter actin dynamics with respect to cytoskeletal changes induced by Rho-GTPase, phospholipids, and tyrosine kinase (Src) mediated signaling [ 45 ].…”