Abstract
As a c-fms-interacting protein, we cloned a novel adaptor molecule, signal-transducing adaptor protein-2 (STAP-2), which contains pleckstrin homology- and Src homology 2-like (PH and SRC) domains and a proline-rich region. STAP-2 is structurally related to STAP-1/BRDG1 (BCR downstream signaling-1), which we had cloned previously from hematopoietic stem cells. STAP-2 is a murine homologue of a recently identified adaptor molecule, BKS, a substrate of BRK tyrosine kinase. STAP-2 was tyrosine-phosphorylated and translocated to the plasma membrane in response to epidermal growth factor when overexpressed in fibroblastic cells. To define the function of STAP-2, we generated mice lacking the STAP-2 gene. STAP-2 mRNA was strongly induced in the liver in response to lipopolysaccharide and in isolated hepatocytes in response to interleukin-6. In the STAP-2(-/-) hepatocytes, the interleukin-6-induced expression of acute-phase (AP) genes and the tyrosine-phosphorylation level of STAT3 were reduced specifically at the late phase (6-24 h) of the response. These data indicate that STAP-2 plays a regulatory role in the AP response in systemic inflammation. STAP-2 contains a YXXQ motif in the C-terminal region that is a potential STAT3-binding site. Overexpression of wild-type STAP-2, but not of mutants lacking this motif, enhanced the AP response element reporter activity and an AP protein production. These data suggest that STAP-2 is a new class of adaptor molecule that modulates STAT3 activity through its YXXQ motif.
Highlights
As a c-fms-interacting protein, we cloned a novel adaptor molecule, signal-transducing adaptor protein-2 (STAP-2), which contains pleckstrin homology- and Src homology 2-like (PH and SRC) domains and a prolinerich region
Because STAP-2 is expressed in a variety of tissues, we changed the definition of STAP to signal-transducing adaptor protein
We found that STAP-2, rather than MAP kinase, is involved in the activation of STAT3
Summary
As a c-fms-interacting protein, we cloned a novel adaptor molecule, signal-transducing adaptor protein-2 (STAP-2), which contains pleckstrin homology- and Src homology 2-like (PH and SRC) domains and a prolinerich region. Overexpression of wild-type STAP-2, but not of mutants lacking this motif, enhanced the AP response element reporter activity and an AP protein production These data suggest that STAP-2 is a new class of adaptor molecule that modulates STAT3 activity through its YXXQ motif. Activated receptor tyrosine kinases trans-phosphorylate several tyrosines in their cytoplasmic domains, which provide recognition sites for various adaptor and effector proteins in multiple signal transduction pathways [1, 2]. These adaptor proteins utilize their Src. The nucleotide sequence(s) reported in this paper has been submitted to GenBankTM/EBI Data Bank with the accession number(s) AW049765. A mutation in the sequence Y933VPL, present in c-Eyk, which is a member of the Axl/Tyro
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