Biochemical characterization of a c-Met (hepatocyte growth factor receptor) clinical variant and implications for drug discovery

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c-Met, the receptor for hepatocyte growth factor, plays an essential role in tumorigenesis and several other aspects of physiology. Several clinical variants of c-Met resulting from genetic mutations have been identified in different types of primary tumors and metastatic lesions. Analysis of mutations in the human c-Met gene has been extensively carried out in kidney tumors. In addition, c-Met clinical variants have been mainly characterized with respect to their ability to induce transformation and tumorigenesis in preclinical models. It is not clear how these mutations influence the biochemical and structural properties of c-Met and subsequently alter its physiological functions. In this study, we have characterized the cytoplasmic domain of a clinical c-Met variant (M1268T), which has been shown to exhibit a very strong transforming ability. The results of this study show that the M1268T clinical variant exhibits a significantly higher affinity for ATP and a higher V_max than those of wild type c-Met as revealed by an in vitro biochemical autophosphorylation assay. This variant enzyme also exhibits an altered dependency for Mg⁺⁺ and Mn⁺⁺ as compared with the wild type enzyme. Finally, this variant is significantly more resistant to inhibition by a c-Met inhibitor in clinic. Taken together, the results of this study have important implications in the understanding of how mutations in c-Met influence the interactions of the enzyme with its substrates and inhibitors.