Elucidation of the Transcriptional Regulation of the Dense Core Vesicle Protein IA-2: CREB and CREB-Related Binding Sites

Thursday, October 11, 2012 — Poster Session III
10:00 a.m. – Noon	Natcher Conference Center, Building 45	NIDCR	ENDOC-3

* FARE Award Winner

Authors

• T Cai
• H Hirai
• A Notkins

Abstract

IA-2 is a transmembrane protein found in the dense core vesicles (DCVs) of neuroendocrine cells and a major autoantigen in type 1 diabetes. DCVs are involved in the secretion of hormones (e.g., insulin) and neurotransmitters. Stimulation of pancreatic beta cells with glucose up-regulates the expression of IA-2 and an increase in IA-2 results in an increase in the number of DCVs. Little is known, however, about IA-2 promoter or transcriptional factors that regulate the expression of IA-2. In the present study we prepared a serial length of IA-2 promoter fragments (−1300 to +115) and linked them to a luciferase reporter. By this approach we have identified a short region (-216 to +1) that has strong promoter activity. We also identified a transcription factor (CREB: cAMP Responsive Element Binding Protein) which binds to two CREB-related sites, located in this region. The binding of CREB to these sites enhances IA-2 transcription 5-to-10 fold. In addition we have confirmed these findings by site-directed mutagenesis, chromatin immunoprecipitation (ChIP) assays and RNAi inhibition. Based on these and other still on-going experiments we believe that IA-2 expression operates through the PKA pathway, which is a critical signaling pathway in glucose-induced insulin secretion.

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