|
|
|
|
|
|
|
||
© The Rockefeller University Press,
0021-9525/1999//1419 $5.00
The Journal of Cell Biology, Volume 147, Number 7,
, 1999 1419-1430
Original Article |
Primary Megakaryocytes Reveal a Role for Transcription Factor Nf-E2 in Integrin 
iibβ3 Signaling
shattil{at}scripps.edu
Platelet integrin
IIbβ3 responds to intracellular signals by binding fibrinogen and triggering cytoskeletal reorganization, but the mechanisms of IIbβ3 signaling remain poorly understood. To better understand this process, we established conditions to study IIbβ3 signaling in primary murine megakaryocytes. Unlike platelets, these platelet precursors are amenable to genetic manipulation. Cytokine-stimulated bone marrow cultures produced three arbitrary populations of IIbβ3-expressing cells with increasing size and DNA ploidy: small progenitors, intermediate-size young megakaryocytes, and large mature megakaryocytes. A majority of the large megakaryocytes bound fibrinogen in response to agonists, while almost none of the smaller cells did. Fibrinogen binding to large megakaryocytes was inhibited by Sindbis virus-mediated expression of isolated β3 integrin cytoplasmic tails. Strikingly, large megakaryocytes from mice deficient in the transcription factor NF-E2 failed to bind fibrinogen in response to agonists, despite normal surface expression of IIbβ3. Furthermore, while megakaryocytes from wild-type mice spread on immobilized fibrinogen and exhibited filopodia, lamellipodia and Rho-dependent focal adhesions and stress fibers, NF-E2–deficient megakaryocytes adhered poorly. These studies establish that agonist-induced activation of IIbβ3 is controlled by NF-E2–regulated signaling pathways that mature late in megakaryocyte development and converge at the β3 cytoplasmic tail. Megakaryocytes provide a physiologically relevant and tractable system for analysis of bidirectional IIbβ3 signaling.
Key Words: IIbβ3 • integrin • megakaryocyte • NF-E2 • signaling
© 1999 The Rockefeller University Press
The first two authors contributed equally to this work.Abbreviations used in this paper: CAT, chloramphenicol acyltransferase; TPO, thrombopoietin.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
|
|
