Pathway: ABC transporters in lipid homeostasis
Reactions in pathway: ABC transporters in lipid homeostasis :
ABC transporters in lipid homeostasis
A defined subset of the ABC transporter superfamily, the ABCA transporters, are highly expressed in monocytes and macrophages and are regulated by cholesterol flux which may indicate their role in in chronic inflammatory diseases (Schmitz and Kaminski 2001, Schmitz et al. 2000). Some D and G members of the ABC transporter family are also important in lipid transport (Voloshyna & Reiss 2011, Morita & Imanaka 2012, Morita et al. 2011).
The ATP-binding cassette (ABC) superfamily of active transporters involves a large number of functionally diverse transmembrane proteins. They transport a variety of compounds through membranes against steep concentration gradients at the cost of ATP hydrolysis. These substrates include amino acids, lipids, inorganic ions, peptides, saccharides, peptides for antigen presentation, metals, drugs, and proteins. The ABC transporters not only move a variety of substrates into and out of the cell, but are also involved in intracellular compartmental transport. Energy derived from the hydrolysis of ATP is used to transport the substrate across the membrane against a concentration gradient. Human genome contains 48 ABC genes; 16 of these have a known function and 14 are associated with a defined human disease (Dean et al. 2001, Borst and Elferink 2002, Rees et al. 2009).
By definition cells have a critical separation between inner (cytoplasmic) and outer (extracellular) compartments. This separation provides for protection, gradient assembly, and environmental control but at the same time isolates the interior compartments of the cell from energy resources, oxygen, and raw materials. Cells have evolved a myriad of mechanisms to regulate, and enable transportation of small molecules ascross plasma membranes and between cellular organelle compartments within cells.