Lipid metabolism plays a pivotal role in maintaining systemic lipid homeostasis and preventing the development of atherosclerotic cardiovascular diseases. Within this network, apolipoprotein A-I (apoA-I) and lecithin-cholesterol acyltransferase (LCAT) are key players in reverse cholesterol transport (RCT). Dysfunctions in these processes, as highlighted by rare disorders such as LCAT deficiencies and Tangier disease, can significantly disrupt the delicate balance of lipid metabolism, ultimately impacting the development of cardiovascular diseases. Our focus is to understand the mechanistic principles that govern the functioning of LCAT and its activation promoting apoA-I mimetic peptides and small positive allosteric modulators.
ApoA-I mimetic peptides, synthetic peptides that mimic the structure and function of apoA-I, have shown promising potential in promoting reverse cholesterol transport and reducing atherosclerosis progression in animal studies. These peptides interact with ATP-binding cassette transporters (ABCA1 and ABCG1), facilitating cholesterol efflux from peripheral tissues to high-density lipoproteins (HDL). Additionally, they can activate LCAT to varying degrees. However, the atom-scale mechanisms underlying these processes remain poorly understood
Positive allosteric modulators (PAMs) are compounds that enhance the catalytic activity of a target protein by binding to an allosteric site distinct from the active site. In the context of LCAT, PAMs have emerged as potential therapeutics to augment its enzymatic function. PAMs bind to specific allosteric site, the membrane binding domain, on LCAT However, the exact atomistic interactions and conformational changes induced by PAMs to promote LCAT action remain unknown, and unraveling these details could provide valuable insights for the design of more effective therapeutics against LCAT deficiencies.
Our research group aims to understanding the mechanistic principles underlying the activation of LCAT by apoA-I mimetic peptides and positive allosteric modulators. Our long term goal is to develop novel or improved therapeutics that can restore impaired LCAT function or boost RCT in dyslipidemic states.
Nanodiscs, which are discoidal lipid bilayers stabilized by membrane scaffold proteins, have emerged as invaluable tools for investigating the intricate structure and function of membrane-associated proteins. Beyond basic research, they also hold promise for pharmaceutical applications, including use as HDL-mimetic particles, drug-delivery vehicles, and imaging agents. In addition to MSP and apoA-I proteins, short amphiphilic peptides (apoA-I mimetic peptides) can be used to produce HDL-mimetic nanodiscs in vitro.
Over the years, many apoA-I mimetic peptides have been designed to replicate key functional properties of apoA-I, such as promoting cholesterol efflux, activating LCAT, and providing antioxidative effects for the treatment of cardiovascular disease. However, the precise arrangement of apoA-I mimetic peptides along the rim of nanodiscs remains largely unclear, limiting our understanding of how these structures influence functional outcomes—particularly in terms of plasma stability and interactions with cellular receptors and plasma enzymes.
Consequently, our research aims to unravel the structural and functional properties of nanodiscs composed of apoA-I mimetic peptides and lipids. By gaining mechanistic insights into these systems, we aim to optimize their therapeutic potential for treating dyslipidemias and enabling targeted drug-delivery applications.
Cholesterol efflux transporters such as ABCA1 and ABCG1 promote the transfer of cholesterol to discoidal and spherical high-density lipoproteins, respectively. In addition, intracellular enzymes such as CES1 play a crucial role in converting esterified cholesterol into free cholesterol during cholesterol efflux from macrophages. The efficiency of these transporters and the hydrolysis of cholesterol esters are closely linked to the development of cardiovascular disease. Our aim is to understand, at a mechanistic level, how these transporters and enzymes function in order to design pharmaceuticals that enhance their activity.