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The lectin Jacalin induces human B‐lymphocyte apoptosis through glycosylation‐dependent interaction with CD45
Author(s) -
Ma Bruce Yong,
Yoshida Kaori,
Baba Makoto,
aka Motohiro,
Matsumoto Shogo,
Kawasaki Nobuko,
Asano Shinji,
Kawasaki Toshisuke
Publication year - 2009
Publication title -
immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.297
H-Index - 133
eISSN - 1365-2567
pISSN - 0019-2805
DOI - 10.1111/j.1365-2567.2008.02977.x
Subject(s) - jacalin , protein tyrosine phosphatase , lyn , tyrosine phosphorylation , microbiology and biotechnology , biology , receptor , chemistry , lectin , phosphorylation , biochemistry , proto oncogene tyrosine protein kinase src
Summary It has been well established that CD45 is a key receptor‐type protein tyrosine phosphatase (PTPase) regulating Src‐family protein tyrosine kinase (Src‐PTK) in T and B lymphocytes. However, precisely how CD45 exerts its effect in these lymphocytes remains controversial. We recently reported that Jacalin, an α‐ O ‐glycoside of the disaccharide Thomsen–Friedenreich antigen‐specific lectin from jackfruit seeds, caused marked T‐cell activation in response to T‐cell receptor ligation and CD28 costimulation by binding to CD45. On extending the reported research, we found that CD45 and isoforms are major Jacalin receptors on B lymphocytes, and that the glycosylation of CD45 is involved in the interaction of Jacalin with the PTPase. In contrast to Jacalin‐stimulated T‐cell activation, we found that Jacalin induced human B‐lymphocyte apoptosis, resulting in calcium mobilization and calpain activation, suggesting that the calcium–calpain pathway may mediate the Jacalin‐induced apoptosis. Importantly, the apoptosis was effectively blocked by a specific CD45 PTPase inhibitor, indicating that Jacalin induces human B‐lymphocyte apoptosis through CD45 triggering. Furthermore, we found that Jacalin significantly increased the C‐terminal inhibitory tyrosine (Tyr507) phosphorylation of Src‐PTK Lyn, one of the major substrates of CD45 PTPase, and this effect was also observed on incubation of B lymphocytes with the specific CD45 PTPase inhibitor, suggesting that Jacalin stimulation results in increasing C‐terminal tyrosine phosphorylation of the kinase through inhibition of CD45 tyrosine phosphatase activity in human B lymphocytes. Therefore, the down‐modulation of Lyn kinase may play a role in the regulation of B‐lymphocyte viability.