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Widespread genomic instability mediated by a pathway involving glycoprotein Ib alpha and Aurora B kinase.

ABSTRACT: c-Myc (Myc) oncoprotein induction of genomic instability (GI) contributes to its initial transforming function and subsequent tumor cell evolution. We describe here a pathway by which Myc, via its target protein glycoprotein Ibalpha (GpIb alpha), mediates GI. Proteomic profiling revealed that the serine/threonine kinase Aurora B is down-regulated by GpIb alpha in p53-deficient primary human fibroblasts. The phenotypes of Aurora B deficiency are strikingly reminiscent of Myc or GpIb alpha overexpression and include double-stranded DNA breaks, altered nuclear size and morphology, chromatin bridges, cleavage furrow regression, and tetraploidy. During mitosis, GpIb alpha and Aurora B redistribute to the cleavage furrow along with other cleavage furrow proteins. GpIb alpha overexpression at levels comparable with those seen in some tumor cells causes the dispersal of these proteins but not Aurora B, resulting in furrow regression and cytokinesis failure. Aurora B normalization redirects the mislocalized furrow proteins to their proper location, corrects the cleavage furrow abnormalities, and restores genomic stability. Aurora B thus appears necessary for a previously unrecognized function in guiding and positioning a number of key proteins, including GpIb alpha to the cleavage furrow. These findings underscore the importance of maintaining a delicate balance among cleavage furrow-associated proteins during mitosis. Suppression of Aurora B via GpIb alpha provides a unifying and mechanistic explanation for several types of Myc-mediated GI.

SUBMITTER: Li Y

PROVIDER: S-EPMC2857109 | biostudies-literature | 2010 Apr

REPOSITORIES: biostudies-literature

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Widespread genomic instability mediated by a pathway involving glycoprotein Ib alpha and Aurora B kinase.

Li Youjun Y Xu Fengfeng L FL Lu Jie J Saunders William S WS Prochownik Edward V EV

The Journal of biological chemistry 20100215 17

c-Myc (Myc) oncoprotein induction of genomic instability (GI) contributes to its initial transforming function and subsequent tumor cell evolution. We describe here a pathway by which Myc, via its target protein glycoprotein Ibalpha (GpIb alpha), mediates GI. Proteomic profiling revealed that the serine/threonine kinase Aurora B is down-regulated by GpIb alpha in p53-deficient primary human fibroblasts. The phenotypes of Aurora B deficiency are strikingly reminiscent of Myc or GpIb alpha overexp ...[more]

PMID: 20157117

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Project description:The proteolytic activity of the neutrophil serine-proteinase cathepsin G (CG) on platelet adherence receptors, the glycoprotein (GP) Ib-IX complex and the integrin alpha IIb beta 3, has been investigated. In the range 50 to 200 nmol/l, CG is a potent platelet agonist which induces shape change, granule exocytosis and aggregation. Investigation of the proteolysis of the receptors' subunits during the course of platelet activation by CG was performed by immunoblot analysis of platelet proteins using a panel of specific antibodies. Exposure of platelets for 3 min at 37 degrees C to CG at a concentration that induces full cell activation resulted in an extensive cleavage of the N-terminal region of the extracellular domain of GPIb alpha, the largest (relative molecular mass, M(r), 143,000) of the three subunits constituting the GPIb-IX complex. In contrast, no detectable proteolytic modification of the two other subunits, GPIb beta and GPIX, was detected. Similarly, we observed that neither of the two subunits of the alpha IIb beta 3 receptor were proteolytically modified by CG. Cleavage of GPIb alpha by CG leaves a remnant of the polypeptide chain with M(r) approx. 106,000 in the plasma membrane, while releasing into the extracellular milieu the N-terminal domain with M(r) in the range 40,000 to 46,000. N-terminal sequencing of the CG-derived fragments of GPIb alpha indicated that the Leu275-Tyr276 peptide bond was the primary cleavage site for this proteinase. Proteolysis of GPIb alpha was already detectable at concentrations of CG as low as 25 nmol/l, while with 200 nmol/l the cleavage was detected as soon as 10 s after exposure of platelets to the proteinase. Comparison of the kinetics and concentration dependency for the proteolysis of GPIb alpha and for the activation of platelets by CG showed that cleavage of the GPIb-IX receptor is an early event that accompanies exocytosis and aggregation. Quantitative evaluation of the conversion of GPIb alpha into its membrane fragment indicated that, under optimal conditions, a maximum of approx. 50% of the total GPIb alpha can be affected by proteolysis. However, this proteolysis was > 90% complete when platelets were in the presence of the potent antagonist prostacyclin, suggesting that cellular redistribution of the GPIb-IX receptor may also occur during activation by CG. These results thus indicate that the very early phase of platelet activation by CG is accompanied by extensive modifications in the structure and expression of the GPIb-IX receptor, an effect that might be of functional significance for the interaction of platelets with the vessel wall.

Dataset Information

Widespread genomic instability mediated by a pathway involving glycoprotein Ib alpha and Aurora B kinase.

Publications

Widespread genomic instability mediated by a pathway involving glycoprotein Ib alpha and Aurora B kinase.

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