A new alternative transcript encodes a 60 kDa truncated form of integrin β3

Abstract

A cDNA for integrin beta 3 isolated from a human erythroleukaemia (HEL) cell library contained a 340 bp insert at position 1281. This mRNA, termed beta 3c, results from the use of a cryptic AG donor splice site in intron 8 of the beta 3 gene, and is different from a previously described alternative beta 3 mRNA. The predicted open reading frame of beta 3C stops at a TAG stop codon 69 bp downstream from position 1281. It starts with the signal peptide and the 404 N-terminal extracellular residues of beta 3, encompassing the ligand binding sites, followed by 23 C-terminal intron-derived residues, corresponding to a truncated form of beta 3 lacking the cysteine-rich, transmembrane and cytoplasmic domains. Expression of beta 3C mRNA was demonstrated in human platelets, megakaryocytes, endothelial cells and HEL cells by reverse transcriptase/PCR. The beta 3C transcript was also demonstrated in the mouse, suggesting its conservation through evolution. Finally, a 60 kDa polypeptide corresponding to the beta 3C alternative transcript was demonstrated in platelets by Western blotting using a polyclonal antibody raised against a synthetic peptide designed from the beta 3C intronic sequence. Taken together, these results suggest a biological role for beta 3C, the first alternative transcript showing an altered extracellular domain of a beta integrin.

The zebrafish vitronectin receptor: Characterization of integrin αV and β3 expression patterns in early vertebrate development

“…These Northern profiles suggest that there are no noticeable changes in ␣V or ␤3 mRNA processing during early stages of zebrafish development. However, due to limitations of Northern analysis, we cannot exclude small splice variants such as those reported for ␤3 in human cancer cell lines (van Kuppevelt et al, 1989;Djaffar et al, 1994).…”

“…These analyses allowed us to determine the integrity of their transcripts, because it is known that integrins have alternatively spliced variants (Fitzgerald et al, 1987;van Kuppevelt et al, 1989;Bray et al, 1990;Djaffar et al, 1994;Fornaro and Languino, 1997). Northern hybridization was performed with total RNAs that were extracted from embryos at 0.5, 1.5, 2.5, and 3.5 days post-fertilization (dpf) (Fig.…”

Identification of Proteins Associating with Glycosylphosphatidylinositol- Anchored T-Cadherin on the Surface of Vascular Endothelial Cells: Role for Grp78/BiP in T-Cadherin-Dependent Cell Survival

“…This might be an artifact related to partial protein degradation during immunoprecipitation and preparation of samples for sequencing. However, as shown for human platelets, where a 60-kDa polypeptide corresponding to the integrin ␤ 3C alternative transcript was detected (14), the presence of alternative integrin ␤ 3 isoforms in EC is possible. Ongoing studies in our laboratory are aimed at determining the impact of integrin ␤ 3 -T-cad interactions in promigratory and proangiogenic signaling.…”

Natural selection driven by DNA binding proteins shapes genome-wide motif statistics

“…Protein assays have confirmed the expression of truncated ITGB3 protein in platelets. 89 Platelets contain multiple forms of the low-affinity immunoglobulin Fc region receptor IIa mRNA. Variants with and without the transmembrane exon are detected at approximately equal proportions in platelets.…”

“…[85][86][87] Correspondingly, soluble P-selectin is found in the nonmembrane fraction of platelets, totaling up to 10% of total P-selectin levels. 88 Splice variants of ITGB3 89 code for a truncated protein, with the transmembrane and cytoplasmic domains missing. Protein assays have confirmed the expression of truncated ITGB3 protein in platelets.…”