His499 Regulates Dimerization and Prevents Oncogenic Activation by Asparagine Mutations of the Human Thrombopoietin Receptor.
(2015) Journal of Biological Chemistry — Vol. 291, n° 6, p. 1317-1324 (2015)
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- (en) Ligand binding to the extracellular domain of the thrombopoietin receptor (TpoR) imparts a specific orientation on the receptors' transmembrane (TM) and intracellular domains that is required for physiologic activation via receptor dimerization. To map the inactive and active dimeric orientations of the TM helices, we performed asparagine (Asn) scanning mutagenesis of the TM domains of the murine and human TpoR. Substitution of Asn at only one position (S505N) activated the human receptor, while Asn substitutions at several positions activated the murine receptor. Second-site mutational studies indicate that His499 near the N-terminus of the TM domain is responsible for protecting the human receptor from activation by asparagine mutations. Structural studies reveal that the sequence preceding His499 is helical in the murine receptor, but non-helical in peptides corresponding to the TM domain of the inactive human receptor. The activating S505N mutation and the small molecule agonist eltrombopag both induce helix in this region of the TM domain, and are associated with dimerization and activation of the human receptor. Thus, His499 provides additional protection against activating mutations, such as oncogenic asparagine mutations in the TM domain, and regulates the activation of human TpoR. Stefan N. Constantinescu and Steven O. Smith are co-last Author
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Leroy, E., Defour, J.-P., Sato, T., Dass, S., Gryshkova, V., Shwe, M. M., Staerk, J., Constantinescu, S., & Smith, S. O. (2015). His499 Regulates Dimerization and Prevents Oncogenic Activation by Asparagine Mutations of the Human Thrombopoietin Receptor. Journal of Biological Chemistry, 291(6), 1317-1324. https://doi.org/10.1074/jbc.M115.696534 (Original work published 2015)