7sjp
From Proteopedia
anti-HtrA1 Fab15H6.v4 bound to HtrA1-LoopA peptide
Structural highlights
DiseaseHTRA1_HUMAN Variations in the promoter region of HTRA1 are the cause of susceptibility to age-related macular degeneration type 7 (ARMD7) [MIM:610149. ARMD is the leading cause of vision loss and blindness among older individuals in the developed word. It is classified as either dry (nonneovascular) or wet (neovascular). ARMD7 is a wet form, in which new blood vessels form and break beneath the retina. This leakage causes permanent damage to surrounding retinal tissue, distorting and destroying central vision. Wet ARMD is more prevalent among Asians than Caucasians.[1] [2] Defects in HTRA1 are the cause of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL) [MIM:600142. CARASIL is characterized by nonhypertensive cerebral small-vessel arteriopathy with subcortical infarcts, alopecia, and spondylosis, with an onset in early adulthood. On neuropathological examination, atherosclerosis associated with intimal thickening and dense collagen fibers, loss of vascular smooth-muscle cells, and hyaline degeneration of the tunica media has been observed in cerebral small arteries.[3] FunctionHTRA1_HUMAN Serine protease with a variety of targets, including extracellular matrix proteins such as fibronectin. HTRA1-generated fibronectin fragments further induce synovial cells to up-regulate MMP1 and MMP3 production. May also degrade proteoglycans, such as aggrecan, decorin and fibromodulin. Through cleavage of proteoglycans, may release soluble FGF-glycosaminoglycan complexes that promote the range and intensity of FGF signals in the extracellular space. Regulates the availability of insulin-like growth factors (IGFs) by cleaving IGF-binding proteins. Inhibits signaling mediated by TGF-beta family members. This activity requires the integrity of the catalytic site, although it is unclear whether TGF-beta proteins are themselves degraded. By acting on TGF-beta signaling, may regulate many physiological processes, including retinal angiogenesis and neuronal survival and maturation during development. Intracellularly, degrades TSC2, leading to the activation of TSC2 downstream targets.[4] [5] [6] Publication Abstract from PubMedThe trimeric serine protease HTRA1 is a genetic risk factor associated with geographic atrophy (GA), a currently untreatable form of age-related macular degeneration. Here, we describe the allosteric inhibition mechanism of HTRA1 by a clinical Fab fragment, currently being evaluated for GA treatment. Using cryo-EM, X-ray crystallography and biochemical assays we identify the exposed LoopA of HTRA1 as the sole Fab epitope, which is approximately 30 A away from the active site. The cryo-EM structure of the HTRA1:Fab complex in combination with molecular dynamics simulations revealed that Fab binding to LoopA locks HTRA1 in a non-competent conformational state, incapable of supporting catalysis. Moreover, grafting the HTRA1-LoopA epitope onto HTRA2 and HTRA3 transferred the allosteric inhibition mechanism. This suggests a conserved conformational lock mechanism across the HTRA family and a critical role of LoopA for catalysis, which was supported by the reduced activity of HTRA1-3 upon LoopA deletion or perturbation. This study reveals the long-range inhibition mechanism of the clinical Fab and identifies an essential function of the exposed LoopA for activity of HTRA family proteases. Allosteric inhibition of HTRA1 activity by a conformational lock mechanism to treat age-related macular degeneration.,Gerhardy S, Ultsch M, Tang W, Green E, Holden JK, Li W, Estevez A, Arthur C, Tom I, Rohou A, Kirchhofer D Nat Commun. 2022 Sep 5;13(1):5222. doi: 10.1038/s41467-022-32760-9. PMID:36064790[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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