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pubmed:abstractText |
CD40 is a receptor that is critical for the survival, growth, differentiation, and isotype switching of B lymphocytes. Although CD40 lacks intrinsic tyrosine kinase activity, its ligation induces protein tyrosine phosphorylation, which is necessary for several CD40-mediated events. We show that engagement of CD40 induces tyrosine phosphorylation and activation of Jak3 as well as of STAT3. Jak3 is constitutively associated with CD40, and this interaction requires a proline-rich sequence in the membrane-proximal region of CD40. Deletion of this sequence abolishes the capacity of CD40 to induce expression of CD23, ICAM-1, and lymphotoxin-alpha genes in B cells. These results indicate that signaling through Jak3 is activated by CD40 and plays an important role in CD40-mediated functions.
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pubmed:affiliation |
Children's Hospital, Department of Pediatrics, Harvard Medical School, Boston, Massachusetts 02115, USA.
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