Identification of arrestin-like proteins in a human megakaryocytic cell line (HEL cells)

Proteins of the arrestin family contribute to the regulation of G-protein-mediated signal transduction in a number of tissues, possibly by a desensitization of the appropriate receptor(s). In this study we demonstrate the presence of arrestin-related proteins in a megakaryoblast-like cell line (HEL). Mouse monoclonal and rabbit polyclonal antibodies were prepared against visual arrestin, against a synthetic peptide'GFLGELTSSEVATEVPFRLM' (a pathogenic sequence corresponding to residues 340 to 359 of human visual arrestin), and against the peptide 'VDTNLIEFDTNDDDIV' that represents an aminoacid sequence present in beta -arrestins 1 and 2 but absent from visual arrestin. In Western blots, all of these antibodies revealed a 48-kDa protein in HEL cell extract. Using a beta-arrestin specific primer, RT-PCR of RNA from HEL cells confirmed the presence of beta-arrestin mRNA, with a predicted 480 bp having 98.8% homology with beta-arrestin. These results suggest that arrestin-family proteins may be involved in the desensitization of G-protein mediated receptors in platelets.