5jt2
BRAFV600E Kinase Domain In Complex with Chemically Linked Vemurafenib Inhibitor VEM-BISAMIDE
Structural highlights
DiseaseBRAF_HUMAN Note=Defects in BRAF are found in a wide range of cancers.[1] Defects in BRAF may be a cause of colorectal cancer (CRC) [MIM:114500.[2] Defects in BRAF are involved in lung cancer (LNCR) [MIM:211980. LNCR is a common malignancy affecting tissues of the lung. The most common form of lung cancer is non-small cell lung cancer (NSCLC) that can be divided into 3 major histologic subtypes: squamous cell carcinoma, adenocarcinoma, and large cell lung cancer. NSCLC is often diagnosed at an advanced stage and has a poor prognosis.[3] [4] Defects in BRAF are involved in non-Hodgkin lymphoma (NHL) [MIM:605027. NHL is a cancer that starts in cells of the lymph system, which is part of the body's immune system. NHLs can occur at any age and are often marked by enlarged lymph nodes, fever and weight loss.[5] [6] Defects in BRAF are a cause of cardiofaciocutaneous syndrome (CFC syndrome) [MIM:115150; also known as cardio-facio-cutaneous syndrome. CFC syndrome is characterized by a distinctive facial appearance, heart defects and mental retardation. Heart defects include pulmonic stenosis, atrial septal defects and hypertrophic cardiomyopathy. Some affected individuals present with ectodermal abnormalities such as sparse, friable hair, hyperkeratotic skin lesions and a generalized ichthyosis-like condition. Typical facial features are similar to Noonan syndrome. They include high forehead with bitemporal constriction, hypoplastic supraorbital ridges, downslanting palpebral fissures, a depressed nasal bridge, and posteriorly angulated ears with prominent helices. The inheritance of CFC syndrome is autosomal dominant.[7] Defects in BRAF are the cause of Noonan syndrome type 7 (NS7) [MIM:613706. Noonan syndrome is a disorder characterized by facial dysmorphic features such as hypertelorism, a downward eyeslant and low-set posteriorly rotated ears. Other features can include short stature, a short neck with webbing or redundancy of skin, cardiac anomalies, deafness, motor delay and variable intellectual deficits.[8] [9] Defects in BRAF are the cause of LEOPARD syndrome type 3 (LEOPARD3) [MIM:613707. LEOPARD3 is a disorder characterized by lentigines, electrocardiographic conduction abnormalities, ocular hypertelorism, pulmonic stenosis, abnormalities of genitalia, retardation of growth, and sensorineural deafness.[10] [11] Note=A chromosomal aberration involving BRAF is found in pilocytic astrocytomas. A tandem duplication of 2 Mb at 7q34 leads to the expression of a KIAA1549-BRAF fusion protein with a constitutive kinase activity and inducing cell transformation.[12] FunctionBRAF_HUMAN Involved in the transduction of mitogenic signals from the cell membrane to the nucleus. May play a role in the postsynaptic responses of hippocampal neuron. Publication Abstract from PubMedThe BRAF kinase, within the mitogen activated protein kinase (MAPK) signaling pathway, harbors activating mutations in about half of melanomas and to a significant extent in many other cancers. A single valine to glutamic acid substitution at residue 600 (BRAFV600E) accounts for about 90% of these activating mutations. While BRAFV600E-selective small molecule inhibitors, such as debrafenib and vemurafenib, have shown therapeutic benefit, almost all patients develop resistance. Resistance often arises through reactivation of the MAPK pathway, typically through mutation of upstream RAS, downstream MEK, or splicing variants. RAF kinases signal as homo- and heterodimers, and another complication associated with small molecule BRAFV600E inhibition is drug-induced allosteric activation of a wild-type RAF subunit (BRAF or CRAF) of the kinase dimer, a process called "transactivation" or "paradoxical activation." Here, we used BRAFV600E and vemurafenib as a model system to develop chemically linked kinase inhibitors to lock RAF dimers in an inactive conformation that cannot undergo transactivation. This structure-based design effort resulted in the development of Vem-BisAmide-2, a compound containing two vemurafenib molecules connected by a bis amide linker. We show that Vem-BisAmide-2 has comparable inhibitory potency as vemurafenib to BRAFV600E both in vitro and in cells but promotes an inactive dimeric BRAFV600E conformation unable to undergo transactivation. The crystal structure of a BRAFV600E/Vem-BisAmide-2 complex and associated biochemical studies reveal the molecular basis for how Vem-BisAmide-2 mediates selectivity for an inactive over an active dimeric BRAFV600E conformation. These studies have implications for targeting BRAFV600E/RAF heterodimers and other kinase dimers for therapy. Chemically Linked Vemurafenib Inhibitors Promote an Inactive BRAFV600E Conformation.,Grasso M, Estrada MA, Ventocilla C, Samanta M, Maksimoska J, Villanueva J, Winkler JD, Marmorstein R ACS Chem Biol. 2016 Sep 6. PMID:27571413[13] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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