Anti-IgM induces up-regulation and tyrosine-phosphorylation of heterogeneous nuclear ribonucleoprotein K proteins (hnRNP K) in a Ramos B cell line.
Heterogeneous nuclear ribonucleoprotein K protein (hnRNP K) has diverse molecular partners implicated in signal transduction pathways, and is tyrosine-phosphorylated in response to growth factors and oxidative stress. Among the structurally distinct domains of hnRNP K, an SH3-binding domain (SH3BD) has been known to promote the association of SH3-containing tyrosine kinases and protooncoprotein Vav, which are involved in B cell receptor (BCR) signalling. In this study, we analyzed proteins of Ramos B cell line that are altered upon BCR activation with anti-IgM antibody, revealing that a certain hnRNP K isoform is up-regulated in response to anti-IgM treatment. We also showed that hnRNP K is tyrosine-phosphorylated after BCR ligation. HnRNP K lacking the SH3BD is shown not to interact with phosphorylated Vav, and Ramos cells stably expressing this mutant protein are less susceptible to anti-IgM-induced apoptosis, indicating that hnRNP K is coupled to BCR-mediated signalling and its SH3BD is required for proper signal propagation. Our results provide the first evidence that hnRNP K is involved in BCR signalling pathway.
Jeon
Hye-Kyung
HK
Department of Biology, Yonsei University, Shinchon-dong 134, Seodaemun-gu, Seoul 120-749, Republic of Korea.
Ahn
Jeong-Hun
JH
Choe
Jongseon
J
Park
Jeon Han
JH
Lee
Tae H
TH
D000888:Antibodies, Anti-Idiotypic / Q000494:pharmacology*; D017209:Apoptosis / Q000276:immunology; D001402:B-Lymphocytes / Q000187:drug effects* / Q000378:metabolism*; D045744:Cell Line, Tumor; D015180:Electrophoresis, Gel, Two-Dimensional; D034641:Heterogeneous-Nuclear Ribonucleoprotein K / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology; D010766:Phosphorylation / Q000187:drug effects; D019000:Phosphotyrosine / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects*
D000888:Antibodies, Anti-Idiotypic; D034641:Heterogeneous-Nuclear Ribonucleoprotein K; D007075:Immunoglobulin M; C044203:anti-IgM; D019000:Phosphotyrosine