IDENTIFICATION OF ARRESTIN-LIKE PROTEINS IN A HUMAN MEGAKARYOCYTIC CELL-LINE (HEL CELLS)

Proteins of the arrestin family contribute to the regulation of G-prot ein-mediated signal transduction in a number of tissues, possibly by a desensitization of the appropriate receptor(s), In this study we demo nstrate the presence of arrestin-related proteins in a megakaryoblast- like cell line (HEL). Mouse monoclonal and rabbit polyclonal antibodie s 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 'VDTNLI EFDTNDDDIV' that represents an amino acid sequence present in beta-arr estins 1 and 2 but absent from visual arrestin, In Western blots, all of these antibodies revealed a 48-kDa protein in HEL cell extract, Usi ng a beta-arrestin specific primer, RT-PCR of RNA from HEL cells confi rmed the presence of beta-arrestin mRNA, with a predicted 480 bp havin g 98.8% homology with beta-arrestin, These results suggest that arrest in-family proteins may be involved in the desensitization of G-protein mediated receptors in platelets.