St-Germain Jonathan R, Taylor Paul, Zhang Wen, Li Zhihua, Ketela Troy, Moffat Jason, Neel Benjamin G, Trudel Suzanne, Moran Michael F
Program in Molecular Structure and Function, Hospital for Sick Children, Toronto, Canada; Department of Molecular Genetics, University of Toronto, Canada.
Proteomics. 2015 Jan;15(2-3):419-33. doi: 10.1002/pmic.201400259. Epub 2014 Dec 17.
Aberrant expression and activation of FGFR3 is associated with disease states including bone dysplasia and malignancies of bladder, cervix, and bone marrow. MS analysis of protein-phosphotyrosine in multiple myeloma cells revealed a prevalent phosphorylated motif, D/EYYR/K, derived from the kinase domain activation loops of tyrosine kinases including FGFR3 corresponding to a recognition sequence of protein-tyrosine phosphatase PTPN1. Knockdown of PTPN1 or the related enzyme PTPN2 by RNAi resulted in ligand-independent activation of FGFR3. Modulation of FGFR3 activation loop phosphorylation by both PTPN1 and PTPN2 was a function of receptor trafficking and phosphotyrosine phosphatase (PTP) compartmentalization. The FGFR3 activation loop motif DYYKK(650) is altered to DYYKE(650) in the oncogenic variant FGFR3(K650E) , and consequently it is constitutively fully activated and unaffected by activation loop phosphorylation. FGFR3(K650E) was nevertheless remarkably sensitive to negative regulation by PTPN1 and PTPN2. This suggests that in addition to modulating FGFR3 phosphorylation, PTPN1 and PTPN2 constrain the kinase domain by fostering an inactive-state. Loss of this constraint in response to ligand or impaired PTPN1/N2 may initiate FGFR3 activation. These results suggest a model wherein PTP expression levels may define conditions that select for ectopic FGFR3 expression and activation during tumorigenesis.
FGFR3的异常表达和激活与多种疾病状态相关，包括骨发育异常以及膀胱、宫颈和骨髓的恶性肿瘤。对多发性骨髓瘤细胞中蛋白质磷酸酪氨酸的质谱分析揭示了一种普遍存在的磷酸化基序D/EYYR/K，它源自包括FGFR3在内的酪氨酸激酶的激酶结构域激活环，对应于蛋白质酪氨酸磷酸酶PTPN1的识别序列。通过RNA干扰敲低PTPN1或相关酶PTPN2会导致FGFR3的非配体依赖性激活。PTPN1和PTPN2对FGFR3激活环磷酸化的调节是受体转运和磷酸酪氨酸磷酸酶（PTP）区室化的作用。在致癌变体FGFR3(K650E) 中，FGFR3激活环基序DYYKK(650) 变为DYYKE(650)，因此它被组成性地完全激活，并且不受激活环磷酸化的影响。然而，FGFR3(K650E) 对PTPN1和PTPN2的负调节非常敏感。这表明除了调节FGFR3磷酸化外，PTPN1和PTPN2还通过促进非活性状态来限制激酶结构域。响应配体或PTPN1/N2受损时这种限制的丧失可能会引发FGFR3激活。这些结果提示了一种模型，其中PTP表达水平可能决定了在肿瘤发生过程中选择异位FGFR3表达和激活的条件。
