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Blood, 15 February 2004, Vol. 103, No. 4, pp. 1425-1432. Prepublished online as a Blood First Edition Paper on October 16, 2003; DOI 10.1182/blood-2003-03-0716.
Submitted March 6, 2003
Department of Immunology and Signal Transduction, Tokyo Metropolitan Institute for Neuroscience, Tokyo Metropolitan Organization for Medical Research, Tokyo, Japan; Graduate School of Science, Tokyo Metropolitan University, Tokyo, Japan * Corresponding author; email: yakura{at}tmin.ac.jp.
CD45 is a key tyrosine phosphatase regulating Src-family kinases (Src-PTKs) in lymphocytes; precisely how it exerts its effect remains controversial, however. We previously demonstrated that CD45 negatively regulates Lyn in WEHI-231 B cell line. Here we show that negative regulation by CD45 is physiologically significant in B cells and that some CD45 is constitutively associated with glycolipid-enriched microdomains (GEMs), where it inhibits Src-PTKs by dephosphorylating both the negative and the positive regulatory sites. Upon BCR ligation, however, CD45 dissociates from GEMs within 30 sec, inducing phosphorylation of two regulatory sites and activation of Src-PTKs, but subsequently re-associates with the GEMs within 15 min. Disruption of GEMs with methyl-
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