ABCA1 (ATP-binding cassette sub-family A member 1): ABCA1 is a membrane protein essential for transporting cholesterol and phospholipids from cells to lipid-poor apolipoproteins, forming nascent high-density lipoprotein (HDL) particles. This reverse cholesterol transport process helps maintain cholesterol balance and supports healthy lipid metabolism. ABCA1 is mainly expressed in the liver and in peripheral tissues such as macrophages, where it aids in cholesterol removal, contributing to cardiovascular protection. Mutations or reduced expression of ABCA1 can disrupt lipid homeostasis and increase the risk of atherosclerosis.