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Microparticles are the basic storage units for different proteins in platelet granules

Chi Zhang and Yang Yang
This article has been retracted 121(16):3298

Abstract

Platelets are circulating carriers of numerous proteins including coagulation and inflammation factors, cytokines, and angiogenesis regulatory factors. Understanding how platelets store and organize the proteins is crucial to understanding their role and function in the vast involved pathophysiological events. Therefore, in this study we hypothesized that microparticles are the basic storage units for different proteins in platelet granules. We utilized stimulated emission depletion microscopy to study the ultrastructure of platelets and the protein storage in granules. Our results demonstrated that P-selectin, fibrinogen, platelet factor 4 and vascular endothelial growth factor are all packaged and stored in individual sub-granule vesicles. The four proteins all exhibited ring-like distribution in the vesicles with a diameter of approximately 90 nm. We further discovered that one microparticle stores only one type of proteins. These results supported our hypothesis and have provided novel insights of how platelets systematically store and organize proteins in the granules. These insights have not only reevaluated the ultrastructure of platelets, but also provided a link connecting microparticles and platelets from structure to function and pathologies. The link is believed to benefit the understanding of how platelets regulate their pathophysiological participations, such as inflammation, angiogenesis, and tumor growth.

  • Submitted April 9, 2012.
  • Accepted July 13, 2012.