Differential localization of P-selectin and von Willebrand factor during megakaryocyte maturation

Biotech Histochem. 2010 Apr 28;85(3):157-70. doi: 10.3109/10520290903149612.

Abstract

An important step in megakaryocyte maturation is the appropriate assembly of at least two distinct subsets of alpha-granules. The mechanism that sorts the alpha-granule components into distinct structures and mediates their release in response to specific stimuli is now emerging. P-selectin and von Willebrand factor are two proteins present in the alpha-granules that recognize P-selectin glycoprotein ligand on neutrophils and collagen in the subendothelial matrix. These proteins may play an important role in determining the differential release of the alpha-granule contents in response to external stimuli. If P-selectin and von Willebrand factor are localized in the same or different alpha-granules is not known. To clarify this question, we analyzed by immunoelectron microscopy the localization of von Willebrand factor and P-selectin during the maturation of wild-type and Gata1(low) megakaryocytes induced in vivo by treating animals with thrombopoietin. Gata1(low) is a hypomorphic mutation that blocks megakaryocyte maturation, reduces the levels of von Willebrand factor expression and displaces P-selectin on the demarcation membrane system. The maturation block induced by this mutation is partially rescued by treatment in vivo with thrombopoietin. In immature megakaryocytes, both wild-type and Gata1(low), the two receptors were co-localized in the same cytoplasmic structures. By contrast, the two proteins were segregated to separate alpha-granule subsets as the megakaryocytes matured. These observations support the hypothesis that P-selectin and von Willebrand factor may ensure differential release of the alpha-granule content in response to external stimuli.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Differentiation*
  • GATA1 Transcription Factor / genetics
  • GATA1 Transcription Factor / metabolism
  • Gene Expression Regulation, Developmental
  • Megakaryocytes / cytology*
  • Megakaryocytes / metabolism*
  • Mice
  • Microscopy, Immunoelectron
  • P-Selectin / metabolism*
  • Recombinant Proteins / genetics
  • Spleen / chemistry
  • Spleen / cytology
  • von Willebrand Factor / metabolism*

Substances

  • GATA1 Transcription Factor
  • Gata1 protein, mouse
  • P-Selectin
  • Recombinant Proteins
  • von Willebrand Factor