5bv7
Crystal structure of human LCAT (L4F, N5D) in complex with Fab of an agonistic antibody
Structural highlights
DiseaseLCAT_HUMAN Fish-eye disease;Familial LCAT deficiency. The disease is caused by mutations affecting the gene represented in this entry. The disease is caused by mutations affecting the gene represented in this entry. FunctionLCAT_HUMAN Central enzyme in the extracellular metabolism of plasma lipoproteins. Synthesized mainly in the liver and secreted into plasma where it converts cholesterol and phosphatidylcholines (lecithins) to cholesteryl esters and lysophosphatidylcholines on the surface of high and low density lipoproteins (HDLs and LDLs). The cholesterol ester is then transported back to the liver. Has a preference for plasma 16:0-18:2 or 18:O-18:2 phosphatidylcholines. Also produced in the brain by primary astrocytes, and esterifies free cholesterol on nascent APOE-containing lipoproteins secreted from glia and influences cerebral spinal fluid (CSF) APOE- and APOA1 levels. Together with APOE and the cholesterol transporter ABCA1, plays a key role in the maturation of glial-derived, nascent lipoproteins. Required for remodeling high-density lipoprotein particles into their spherical forms.[1] Publication Abstract from PubMedDrug discovery opportunities where loss-of-function alleles of a target gene link to a disease-relevant phenotype often require an agonism approach to up-regulate or re-establish the activity of the target gene. Antibody therapy is increasingly recognized as a favored drug modality due to multiple desirable pharmacological properties. However, agonistic antibodies that enhance the activities of the target enzymes are rarely developed since the discovery of agonistic antibodies remains elusive. Here we report an innovative scheme of discovery and characterization of human antibodies capable of binding to and agonizing a circulating enzyme lecithin cholesterol acyltransferase (LCAT). Utilizing a modified human LCAT protein with enhanced enzymatic activity as an immunogen, we generated fully human monoclonal antibodies using the XenoMouseTM platform. One of the resultant agonistic antibodies, 27C3, binds to and substantially enhances the activity of LCAT from humans and cynomolgus macaques. X-ray crystallographic analysis of the 2.45 A LCAT/27C3 complex shows that 27C3 binding does not induce notable structural changes in LCAT. A single administration of 27C3 to cynomolgus monkeys led to a rapid increase of plasma LCAT enzymatic activity and a 35 % increase of the high density lipoprotein cholesterol that was observed up to 32 days post 27C3 administration. Thus, this novel scheme of immunization in conjunction with high throughput screening may represent an effective strategy for discovering agonistic antibodies against other enzyme targets. 27C3 and other agonistic human anti-human LCAT monoclonal antibodies described herein hold potential for therapeutic development for the treatment of dyslipidemia and cardiovascular disease. Agonistic Human Antibodies Binding To Lecithin-Cholesterol Acyltransferase Modulate High Density Lipoprotein Metabolism.,Gunawardane RN, Fordstrom P, Piper DE, Masterman S, Siu S, Liu D, Brown M, Lu M, Tang J, Zhang R, Cheng J, Gates A, Meininger D, Chan J, Carlson T, Walker N, Schwarz M, Delaney J, Zhou M J Biol Chem. 2015 Dec 7. pii: jbc.M115.672790. PMID:26644477[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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