EXPRESSION OF THE RAS-RELATED RAB3A GENE IN HUMAN INSULINOMAS AND NORMAL HUMAN PANCREATIC-ISLETS

To determine the expression of the small-molecular-weight guanosine 5' -triphosphate (GTP)binding protein rab3a in human endocrine pancreatic tissue, total RNA was isolated from five different human insulinomas and from normal human islets. The expression of rab3a was analyzed by Northern blots utilizing a 1,300-bp Eco RI fragment of the cDNA coding for human rab3a. As in the brain, a specific transcript of 1,800 bp w as detected in all insulinomas, though with varying signal intensity. When the northern membranes were rehybridized with a radioactively lab eled insulin probe, a signal was found for all five insulinomas and ce lls of normal islets. In contrast, normal human islets showed no detec table expression of rab3a. In conclusion, rab3a is expressed to a sign ificant degree in human insulinoma tissue but not in normal islets.