The identification, purification, and characterization of a pancreatic beta-cell form of the microtubule adenosine triphosphatase kinesin.

Abstract

Microtubules have been implicated as being necessary for the secretion of insulin from beta-cells, although the mechanism by which cytoplasmic microtubules contribute to the release of insulin is unknown. Kinesin is a microtubule-dependent adenosine triphosphatase (ATPase) that is thought to be responsible for the intracellular transport of vesicles and organelles. In this manuscript, the purification and preliminary characterization of a beta-cell form of kinesin is described. A 120-kilodalton antikinesin-reactive polypeptide was identified on blots when cultured insulinoma tumor cell lines were subjected to immunoblot analysis using monoclonal antibodies specific for the heavy chain of mammalian kinesin. The beta-cell form of kinesin was isolated from solid rat insulinoma tumors by cosedimentation of the kinesin with microtubules from tissue homogenates in the presence of adenylyl-imidodiphosphate. The beta-cell kinesin was further purified by gel filtration chromatography, and then the pure enzyme was characterized using in vitro assays. Although beta-cell kinesin showed little ATPase activity alone, the enzyme exhibited considerable ATP hydrolysis activity in the presence of taxol-stabilized microtubules. Moreover, in motility assays beta-cell kinesin was able to translocate microtubules across microscope coverslips in the presence of Mg(2+)-ATP. In summary, we report the identity of a novel islet beta-cell form of the microtubule-dependent ATPase kinesin and suggest a possible contribution of the microtubule cytoskeleton in insulin secretion.

• Authors: R Balczon, K A Overstreet, R P Zinkowski, A Haynes, M Appel
• Journal: Endocrinology (Endocrinology) Vol. 131 Issue 1 Pg. 331-6 (Jul 1992) ISSN: 0013-7227 [Print] United States
• PMID: 1612013 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Kinesins

Topics

• Animals
• Brain (enzymology)
• Immunoblotting
• Insulinoma (enzymology)
• Islets of Langerhans (enzymology)
• Kinesins (isolation & purification, metabolism, pharmacology)
• Microtubules (drug effects, enzymology, physiology)
• Pancreatic Neoplasms (enzymology)
• Rats
• Tumor Cells, Cultured