The human MAL2 protein has been demonstrated to regulate secretion in kidney epithelial cells in a lipid raft-dependent manner. Further, MAL2 interacts with TPD52, a protein that promotes secretion in rat pancreatic acinar cells. Two MAL2 homologues have recently been identified within rat pancreatic β-cells: MAL2A and MAL2B. This suggested that MAL2 and TPD52 might interact with each other to coordinate secretion within both human kidney epithelial cells and rat pancreatic β-cells. I report here that both <i>MAL2A </i>and <i>MAL2B </i>are expressed within rat pancreatic β-cells. Further, the expression of <i>MAL2B </i>appears to be tightly regulated as sequences within the 5’ UTR of the <i>MAL2B </i>transcript inhibit its translation. Both MAL2A and MAL2B are associated with lipid rafts. Attempts were made to identify interactions between TPD52 and the MAL2 proteins. GST pull-down assays indicated that TPD52 interacts with both MAL2A and MAL2B. This is consistent with previous observations and suggests that TPD52 does not interact with MAL2A or MAL2B via their N-termini, which are distinct between each MAL2 protein. However, a novel <i>Xenopus </i>egg extract interaction assay failed to detect an interaction between TPD52 and the MAL2 proteins. Further, immunohistochemistry indicated that TPD52 did not co-localise and either MAL2A or MAL2B within pancreatic β-cells. These findings indicate that TPD52 and the MAL2 proteins might participate in overlapping secretion pathways. Further, these data suggest that any interaction between TPD52 and the MAL2 proteins might be weak or transient. Finally, initial attempts were made to reduce <i>TPD52 </i>expression within β-cells via RNA silencing in order to elucidate the role of TPD52 in directing secretion. RNA silencing will also be used to examine the role of MAL2A in coordinating secretion.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:439915 |
| Date | January 2006 |
| Creators | Robertson, Lindsay |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=185669 |
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