5u6c
Crystal structure of the Mer kinase domain in complex with a macrocyclic inhibitor
Structural highlights
DiseaseMERTK_HUMAN Defects in MERTK are the cause of retinitis pigmentosa type 38 (RP38) [MIM:613862. RP38 is a retinal dystrophy belonging to the group of pigmentary retinopathies. Retinitis pigmentosa is characterized by retinal pigment deposits visible on fundus examination and primary loss of rod photoreceptor cells followed by secondary loss of cone photoreceptors. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well.[1] FunctionMERTK_HUMAN Receptor tyrosine kinase that transduces signals from the extracellular matrix into the cytoplasm by binding to several ligands including LGALS3, TUB, TULP1 or GAS6. Regulates many physiological processes including cell survival, migration, differentiation, and phagocytosis of apoptotic cells (efferocytosis). Ligand binding at the cell surface induces autophosphorylation of MERTK on its intracellular domain that provides docking sites for downstream signaling molecules. Following activation by ligand, interacts with GRB2 or PLCG2 and induces phosphorylation of MAPK1, MAPK2, FAK/PTK2 or RAC1. MERTK signaling plays a role in various processes such as macrophage clearance of apoptotic cells, platelet aggregation, cytoskeleton reorganization and engulfment. Functions in the retinal pigment epithelium (RPE) as a regulator of rod outer segments fragments phagocytosis. Plays also an important role in inhibition of Toll-like receptors (TLRs)-mediated innate immune response by activating STAT1, which selectively induces production of suppressors of cytokine signaling SOCS1 and SOCS3.[2] Publication Abstract from PubMedThe receptor tyrosine kinase (RTK) family consisting of Tyro3, Axl and Mer (TAM) is one of the most recently identified RTK families. TAM receptors are upregulated postnatally and maintained at high levels in adults. They all play an important role in immunity, but Axl has also been implicated in cancer and therefore is a target in the discovery and development of novel therapeutics. However, of the three members of the TAM family, the Axl kinase domain is the only one that has so far eluded structure determination. To this end, using differential scanning fluorimetry and hydrogen-deuterium exchange mass spectrometry (HDX-MS), we show here that a lower stability and greater dynamic nature of the Axl kinase domain may account for its poor crystallizability. We present the first structural characterization of the Axl kinase domain in complex with a small molecule macrocyclic inhibitor. The Axl crystal structure revealed two distinct conformational states of the enzyme, providing a first glimpse of what an active TAM receptor kinase may look like, and suggesting a potential role for the juxtamembrane region in enzyme activity. We noted that the ATP/inhibitor binding sites of the TAM members closely resemble each other, posing a challenge for the design of a selective inhibitor. We propose that the differences in the conformational dynamics among the TAM family members could potentially be exploited to achieve inhibitor selectivity for targeted receptors. The Axl Kinase Domain in Complex with a Macrocyclic Inhibitor Offers First Structural Insights into an Active TAM Receptor Kinase.,Gajiwala KS, Grodsky N, Bolanos B, Feng J, Ferre R, Timofeevski S, Xu M, Murray BW, Johnson TW, Stewart A J Biol Chem. 2017 Jul 19. pii: jbc.M116.771485. doi: 10.1074/jbc.M116.771485. PMID:28724631[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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