8cpd
Cryo-EM structure of CRaf dimer with 14:3:3
Structural highlights
DiseaseRAF1_HUMAN Defects in RAF1 are the cause of Noonan syndrome type 5 (NS5) [MIM:611553. Noonan syndrome (NS) is a disorder characterized by dysmorphic facial features, short stature, hypertelorism, cardiac anomalies, deafness, motor delay, and a bleeding diathesis. It is a genetically heterogeneous and relatively common syndrome, with an estimated incidence of 1 in 1000-2500 live births.[1] [2] [3] Defects in RAF1 are the cause of LEOPARD syndrome type 2 (LEOPARD2) [MIM:611554. LEOPARD syndrome is an autosomal dominant disorder allelic with Noonan syndrome. The acronym LEOPARD stands for lentigines, electrocardiographic conduction abnormalities, ocular hypertelorism, pulmonic stenosis, abnormalities of genitalia, retardation of growth, and deafness.[4] FunctionRAF1_HUMAN Serine/threonine-protein kinase that acts as a regulatory link between the membrane-associated Ras GTPases and the MAPK/ERK cascade, and this critical regulatory link functions as a switch determining cell fate decisions including proliferation, differentiation, apoptosis, survival and oncogenic transformation. RAF1 activation initiates a mitogen-activated protein kinase (MAPK) cascade that comprises a sequential phosphorylation of the dual-specific MAPK kinases (MAP2K1/MEK1 and MAP2K2/MEK2) and the extracellular signal-regulated kinases (MAPK3/ERK1 and MAPK1/ERK2). The phosphorylated form of RAF1 (on residues Ser-338 and Ser-339, by PAK1) phosphorylates BAD/Bcl2-antagonist of cell death at 'Ser-75'. Phosphorylates adenylyl cyclases: ADCY2, ADCY5 and ADCY6, resulting in their activation. Phosphorylates PPP1R12A resulting in inhibition of the phosphatase activity. Phosphorylates TNNT2/cardiac muscle troponin T. Can promote NF-kB activation and inhibit signal transducers involved in motility (ROCK2), apoptosis (MAP3K5/ASK1 and STK3/MST2), proliferation and angiogenesis (RB1). Can protect cells from apoptosis also by translocating to the mitochondria where it binds BCL2 and displaces BAD/Bcl2-antagonist of cell death. Regulates Rho signaling and migration, and is required for normal wound healing. Plays a role in the oncogenic transformation of epithelial cells via repression of the TJ protein, occludin (OCLN) by inducing the up-regulation of a transcriptional repressor SNAI2/SLUG, which induces down-regulation of OCLN. Restricts caspase activation in response to selected stimuli, notably Fas stimulation, pathogen-mediated macrophage apoptosis, and erythroid differentiation.[5] [6] [7] [8] [9] [10] [11] Publication Abstract from PubMedRAF protein kinases are essential effectors in the MAPK pathway and are important cancer drug targets. Structural understanding of RAF activation is so far based on cryo-electron microscopy (cryo-EM) and X-ray structures of BRAF in different conformational states as inactive or active complexes with KRAS, 14-3-3 and MEK1. In this study, we have solved the first cryo-EM structures of CRAF(2)/14-3-3(2) at 3.4 A resolution and CRAF(2)/14-3-3(2)/MEK1(2) at 4.2 A resolution using CRAF kinase domain expressed as constitutively active Y340D/Y341D mutant in insect cells. The overall architecture of our CRAF(2)/14-3-3(2) and CRAF(2)/14-3-3(2)/MEK1(2) cryo-EM structures is highly similar to corresponding BRAF structures in complex with 14-3-3 or 14-3-3/MEK1 and represent the activated dimeric RAF conformation. Our CRAF cryo-EM structures provide additional insights into structural understanding of the activated CRAF(2)/14-3-3(2)/MEK1(2) complex. Cryo-EM Structures of CRAF(2)/14-3-3(2) and CRAF(2)/14-3-3(2)/MEK1(2) Complexes.,Dedden D, Nitsche J, Schneider EV, Thomsen M, Schwarz D, Leuthner B, Gradler U J Mol Biol. 2024 Mar 15;436(6):168483. doi: 10.1016/j.jmb.2024.168483. Epub 2024 , Feb 7. PMID:38331211[12] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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