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ludc web

Anna Wendt

Assistant researcher

ludc web

Integrator of stress responses calmodulin binding transcription activator 1 (Camta1) Regulates miR-212/miR-132 Expression and insulin secretion

Author

  • Inês Guerra Uerra Mollet
  • Helena Anna Malm
  • Anna Wendt
  • Marju Orho-Melander
  • Lena Eliasson

Summary, in English

Altered microRNA profiles have been demonstrated in experimental models of type 2 diabetes, including in islets of the diabetic Goto-Kakizaki (GK) rat. Our bioinformatic analysis of conserved sequences in promoters of microRNAs, previously observed to be up-regulated in GK rat islets, revealed putative CGCG-core motifs on the promoter of the miR-212/miR-132 cluster, overexpression of which has been shown to increase insulin secretion. These motifs are possible targets of calmodulin binding transcription activators Camta1 and Camta2 that have been recognized as integrators of stress responses. We also identified putative NKE elements, possible targets of NK2 homeobox proteins like the essential islet transcription factor Nkx2-2. As Camtas can function as co-activators with NK2 proteins in other tissues, we explored the role of Camta1, Camta2, and Nkx2-2 in the regulation of the miR-212/miR-132 cluster and insulin secretion. We demonstrate that exposure of control Wistar or GK rat islets to 16.7 mM glucose increases miR-212/miR-132 expression but significantly less so in the GK rat. In addition, Camta1, Camta2, and Nkx2-2 were down-regulated in GK rat islets, and knockdown of Camta1 reduced miR-212/miR-132 promoter activity and miR-212/miR-132 expression, even under cAMP elevation. Knockdown of Camta1 decreased insulin secretion in INS-1 832/13 cells and Wistar rat islets but increased insulin content. Furthermore, knockdown of Camta1 reduced K+-induced insulin secretion and voltage-dependent Ca2+ currents. We also demonstrate Camta1 and Nkx2-2 protein interaction. These results indicate that Camta1 is required not only for expression of the miR-212/miR-132 cluster but at multiple levels for regulating beta cell insulin content and secretion.

Department/s

  • Department of Clinical Sciences, Malmö
  • Department of Clinical Sciences, Lund
  • EXODIAB: Excellence of Diabetes Research in Sweden
  • EpiHealth: Epidemiology for Health

Publishing year

2016-08-26

Language

English

Pages

18440-18452

Publication/Series

Journal of Biological Chemistry

Volume

291

Issue

35

Document type

Journal article

Publisher

ASBMB

Topic

  • Cell and Molecular Biology

Keywords

  • Insulin
  • calmodulin binding
  • bioinformatics
  • rat

Status

Published

ISBN/ISSN/Other

  • ISSN: 0021-9258