SIGNAL-TRANSDUCTION AND GLYCOPHOSPHATIDYLINOSITOL-LINKED PROTEINS (LYN, LCK, CD4, CD45, G-PROTEINS, AND CD55) SELECTIVELY LOCALIZE IN TRITON-INSOLUBLE PLASMA-MEMBRANE DOMAINS OF HUMAN LEUKEMIC-CELL LINES AND NORMAL GRANULOCYTES

Src-family nonreceptor protein tyrosine kinases (NRPTK) are associated with cell surface receptors in large detergent-resistant complexes: i n epithelial cells, yes is selectively located in vesicle structures c ontaining caveolin (''caveolae''). These formations are typically also endowed with glycophosphatidylinositol (GPI)-anchored proteins. In th e present study, we observed lck, lyn, src, hck, CD4, CD45, G proteins , and CD55 (decay-accelerating factor) expression in the buoyant low-d ensity Triton-insoluble (LDTI) fraction of selected leukemic cell line s and granulocytes. We provide a detailed analysis of the two most hig hly expressed NRPTK, p53/p56(lyn) and p56(lck), which are involved in the transduction of signals for proliferation and differentiation of m onocytes/B lymphocytes and T lymphocytes, respectively. We show that l yn is selectively recovered in LDTI complexes isolated from human leuk emic cell lines (promyelocytic [HL-60], erythroid [K562] and B-lymphoi d [697]) and from normal human granulocytes, and that lck is recovered from LDTI fractions of leukemic T- and B-lymphoid cell lines (GEM, 69 7). In LDTI fractions of leukemic cells, lck and lyn are enriched 100- fold as compared with the total cell lysates. Analysis of these fracti ons by electron microscopy shows the presence of 70- to 200-nm vesicle s: lyn and lck are homogenously distributed in the vesicles, as reveal ed by an immunogold labeling procedure. These novel results propose a role for these vesicles in signal transduction mechanisms of normal an d neoplastic hematopoietic cells. In support of this hypothesis, we fu rther observed that molecules participating in B- and T-cell receptor activation cofractionate in the LDTI fractions, CD45/lyn (B cells) and CD45/lck/CD4 (T cells). (C) 1996 by The American Society of Hematolog y.