title: Structural insights into the inhibited states of the Mer receptor tyrosine kinase.
abstract: The mammalian ortholog of the retroviral oncogene v-Eyk, and a receptor tyrosine kinase upstream of antiapoptotic and transforming signals, Mer (MerTK) is a mediator of the phagocytic process, being involved in retinal and immune cell clearance and platelet aggregation. Mer knockout mice are viable and are protected from epinephrine-induced pulmonary thromboembolism and ferric chloride-induced thrombosis. Mer overexpression, on the other hand, is associated with numerous carcinomas. Although Mer adaptor proteins and signaling pathways have been identified, it remains unclear how Mer initiates phagocytosis. When bound to its nucleotide cofactor, the high-resolution structure of Mer shows an autoinhibited alphaC-Glu-out conformation with insertion of an activation loop residue into the active site. Mer complexed with compound-52 (C52: 2-(2-hydroxyethylamino)-6-(3-chloroanilino)-9-isopropylpurine), a ligand identified from a focused library, retains its DFG-Asp-in and alphaC-Glu-out conformation, but acquires other conformational changes. The alphaC helix and DFGL region is closer to the hinge region and the ethanolamine moiety of C52 binds in the groove formed between Leu593 and Val601 of the P-loop, causing a compression of the active site pocket. These conformational states reveal the mechanisms of autoinhibition, the pathophysiological basis of disease-causing mutations, and a platform for the development of chemical probes.
authors.affiliation: Structural Genomics Consortium, University of Toronto, Ont., Canada.
authors.forename: Xudong
authors.initials: X
authors.lastname: Huang
authors.forename: Patrick
authors.initials: P
authors.lastname: Finerty
authors.forename: John R
authors.initials: JR
authors.lastname: Walker
authors.forename: Christine
authors.initials: C
authors.lastname: Butler-Cole
authors.forename: Masoud
authors.initials: M
authors.lastname: Vedadi
authors.forename: Matthieu
authors.initials: M
authors.lastname: Schapira
authors.forename: Sirlester A
authors.initials: SA
authors.lastname: Parker
authors.forename: Benjamin E
authors.initials: BE
authors.lastname: Turk
authors.forename: Debra A
authors.initials: DA
authors.lastname: Thompson
authors.forename: Sirano
authors.initials: S
authors.lastname: Dhe-Paganon
mesh_terms: D000818:Animals; D020134:Catalytic Domain; D004252:DNA Mutational Analysis; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D007107:Immune System; D051379:Mice; D008968:Molecular Conformation; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D010587:Phagocytosis; D011487:Protein Conformation; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry* / Q000378:metabolism; D013927:Thrombosis; D000076202:c-Mer Tyrosine Kinase
chemical_list: D010455:Peptides; D011518:Proto-Oncogene Proteins; C097072:MERTK protein, human; C490767:Mertk protein, mouse; D020794:Receptor Protein-Tyrosine Kinases; D000076202:c-Mer Tyrosine Kinase; D004837:Epinephrine