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Keywords:

  • Kinectin;
  • Intracellular transport;
  • Amylin;
  • Hormone secretion;
  • Islet β-cells

Abstract

Kinectin (KNT) is a candidate membrane receptor for kinesin in the movement of intracellular organelles along microtubules. Isoforms of KNT exist containing different combinations of six small (residues 23–33) variable domains (vd) vd1–6 within the C-terminus. Here we investigate a role for KNT and its isoform KNTvd4 in the transport of amylin and insulin-containing secretory vesicles in the pancreatic islet β-cell line RINm5F. KNTvd4 lacks vd4 that forms the kinesin-binding domain, and hence its role in the cell is an enigma. We report that amylin-containing vesicles also contained insulin, and exhibited microtubule, and small G-protein-dependent secretion. Knockdown of KNT by small interference RNA (siRNA) inhibited amylin expression and secretion. In contrast, recombinant KNTvd4 overexpressed in RINm5F cells associated with amylin-containing vesicles and inhibited amylin secretion, but had no discernible affect on amylin expression. The data suggests that both KNT and KNTvd4 participate in microtubule-dependent secretion of amylin in islet β-cells.