9f31
Crystal structure of MELK with a covalent compound GCL 99
Structural highlights
DiseaseMELK_HUMAN Note=Defects in MELK are associated with some cancers, such as brain or breast cancers. Expression is dramatically increased in aggressive undifferentiated tumors, correlating with poor patient outcome in breast and brain cancers, suggesting a role in tumor-initiating cells and proliferation via its function in cell proliferation regulation. FunctionMELK_HUMAN Serine/threonine-protein kinase involved in various processes such as cell cycle regulation, self-renewal of stem cells, apoptosis and splicing regulation. Has a broad substrate specificity; phosphorylates BCL2L14, CDC25B, MAP3K5/ASK1 and ZNF622. Acts as an activator of apoptosis by phosphorylating and activating MAP3K5/ASK1. Acts as a regulator of cell cycle, notably by mediating phosphorylation of CDC25B, promoting localization of CDC25B to the centrosome and the spindle poles during mitosis. Plays a key role in cell proliferation and carcinogenesis. Required for proliferation of embryonic and postnatal multipotent neural progenitors. Phosphorylates and inhibits BCL2L14, possibly leading to affect mammary carcinogenesis by mediating inhibition of the pro-apoptotic function of BCL2L14. Also involved in the inhibition of spliceosome assembly during mitosis by phosphorylating ZNF622, thereby contributing to its redirection to the nucleus. May also play a role in primitive hematopoiesis.[1] [2] [3] [4] [5] [6] Publication Abstract from PubMedProtein kinases are important drug targets, yet specific inhibitors have been developed for only a fraction of the more than 500 human kinases. A major challenge in designing inhibitors for highly related kinases is selectivity. Unlike their non-covalent counterparts, covalent inhibitors offer the advantage of selectively targeting structurally similar kinases by modifying specific protein side chains, particularly non-conserved cysteines. Previously, covalent fragment screens yielded potent and selective compounds for individual kinases such as ERK1/2 but have not been applied to the broader kinome. Furthermore, many of the accessible cysteine positions have not been addressed so far. Here, we outline a generalizable approach to sample ATP-site cysteines with fragment-like covalent inhibitors. We present the development of a kinase-focused fragment library and its systematic screening against a curated selection of 47 kinases, with 60 active site-proximal cysteines using LC/MS and differential scanning fluorimetry (DSF) assays, followed by hit validation through various complementary techniques. Our findings expand the repertoire of targetable cysteines within protein kinases, provide insight into unique binding modes identified from crystal structures and deliver isoform-specific hits with promising profiles as starting points for the development of highly potent and selective covalent inhibitors. Probing the Protein Kinases' Cysteinome by Covalent Fragments.,Wang G, Seidler NJ, Rohm S, Pan Y, Liang XJ, Haarer L, Berger BT, Sivashanmugam SA, Wydra VR, Forster M, Laufer SA, Chaikuad A, Gehringer M, Knapp S Angew Chem Int Ed Engl. 2024 Dec 24:e202419736. doi: 10.1002/anie.202419736. PMID:39716901[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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