Identification of palladin isoforms and characterization of an isoform-specific interaction between Lasp-1 and palladin.
Palladin is a recently described phosphoprotein with an important role in cytoskeletal organization. The major palladin isoform (90-92 kDa) binds to three actin-associated proteins (ezrin, VASP and alpha-actinin), suggesting that palladin functions as a cytoskeletal scaffold. Here, we describe the organization of the palladin gene, which encodes multiple isoforms, including one (140 kDa) with a similar localization pattern to 90 kDa palladin. Overexpression of the 90 kDa or 140 kDa isoforms in COS-7 cells results in rearrangements of the actin cytoskeleton into super-robust bundles and star-like arrays, respectively. Sequence analysis of 140 kDa palladin revealed a conserved binding site for SH3 domains, suggesting that it binds directly to the SH3-domain protein Lasp-1. Binding of 140 kDa palladin, but not 90 kDa palladin, to Lasp-1 was confirmed by yeast two-hybrid and GST-pull-down assays. Isoform-specific siRNA experiments suggested that 140 kDa palladin plays a role in recruiting Lasp-1 to stress fibers. These results add Lasp-1, an actin-binding protein with a crucial role in cell motility, to the growing list of palladin's binding partners, and suggest that 140 kDa palladin has a specialized function in organizing the actin arrays that participate in cell migration and/or cellular contractility.
Department of Cell and Molecular Physiology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7545, USA.
Andrew S
AS
Rachlin
Carol A
CA
Otey
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D019556:COS Cells; D002522:Chlorocebus aethiops; D003598:Cytoskeletal Proteins / Q000235:genetics* / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D060588:LIM Domain Proteins; D051379:Mice; D008840:Microfilament Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D009928:Organ Specificity; D010750:Phosphoproteins / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D018909:src Homology Domains
D000199:Actins; D003598:Cytoskeletal Proteins; D018398:Homeodomain Proteins; D060588:LIM Domain Proteins; C490692:Lasp1 protein, mouse; D008840:Microfilament Proteins; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D020033:Protein Isoforms; C485873:palladin protein, mouse