Abstract 1876 Study of Serum Albumin Complexation with Bioactive Lipids

Lysophospholipids (LPLs) act as primary or secondary messengers and are also known as bioactive lipids.LPLs act through their cognate G-protein coupled receptors (GPCRs) and have significant roles in intracellular signalling pathways.Due to the diverse ligand-binding capabilities of serum albumins and their abundance in the blood plasma as a transporter protein, it is important to understand how they participate in delivering LPLs to their cognate GPCRs.However, the binding sites and molecular mechanism through which these bioactive lipids are delivered is still unclear.Lysophosphatidic acid (LPA) is a bioactive lipid whose receptor-mediated signalling have shown significance in different physiological processes. .We have used the intrinsic fluorescence property of BSA and HSA to measure and compare their emission intensities caused by binding interactions with three lysophosphatidic acid species (16:0, 18:1 and 20:4 LPA) in the presence and absence of fatty acids.Irrespective of chain length and unsaturation, both LPAs participate in quenching of a tryptophan residue in BSA.However, an unexpected increase in fluorescence signal for HSA coupled with blue shifts in the emission wavelength is observed which contradicts with other reported lysophospholipids (lysophosphatidylcholine, and lysophosphatidylethanolamine) interactions with HSA.This indicates that LPAs have different binding interactions with HSA which can possibly affect their subsequent delivery to and further interaction with GPCRs.