Blood Journal
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Brief report

Quantitative immunofluorescence mapping reveals little functional coclustering of proteins within platelet α-granules

  1. Jeffrey Kamykowski1,
  2. Peter Carlton2,
  3. Siddharth Sehgal1, and
  4. Brian Storrie1
  1. 1Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR; and
  2. 2Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA


Platelets are small anucleate blood cells that aggregate to seal leaks at sites of vascular injury and are important in the pathology of atherosclerosis, acute coronary syndromes, rheumatoid arthritis, cancer, and the regulation of angiogenesis. In all cases, platelet aggregation requires release of stored proteins from α-granules. However, how proteins with potentially antagonistic functions are packaged within α-granules is controversial. One possibility is the packaging of functional agonists and antagonists into different α-granule populations. By quantitative immunofluorescence colocalization, we found that pair-wise comparisons of 15 angiogenic-relevant α-granule proteins displayed little, if any, pattern of functional coclustering. Rather, the data suggested a Gaussian distribution indicative of stochastic protein delivery to individual granules. The apparent physiologic paradox raised by these data may be explained through alternate mechanisms, such as differential content release through incomplete granule fusion or dampened and balanced regulatory networks brought about by the corelease of antagonistic factors.

  • Submitted January 18, 2011.
  • Accepted May 13, 2011.
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