Apoliprotein A-I Helsinki promotes intracellular acyl-CoA Cholesterol acyltransferase

TOLEDO, J. D.; GONZALEZ MARINA CECILIA; CABALEIRO, L.; GARDA, H. A.

Varsovia

Conferencia; 52nd International Conference on the Bioscience of lipids; 2011

ICBL

Apolipoprotein A-I (apoAI) is the major protein of high density lipoproteins (HDL) and plays a relevant role in the antiatherogenic reverse cholesterol transport. This protein is mainly constituted by type A amphipathic a-helical repeats. However, there are two repeats with a particular type Y charge distribution, one within the central domain and the other at the C-terminus, which have been proposed as key role players in the apoAI mediated cell lipid efflux. Patients carrying an apoAI variant with a single deletion at the central type Y helical region (DK107) have an impaired HDL metabolism and increased atherogenic risk. This single deletion could alter the helix registry and modify the lipid binding properties and/or the interactions of the central type Y helix with others cellular proteins. To know if the cellular responses to DK107 are altered, as well as to test the functional role of the central Y helical domain, we have compaired the behavior of DK107 with wild type apoAI and another variant with a deleted Lysine (DK226) in the C-terminal type Y helical repeat. Here, we present results about the responses to these apoAI variants of two cell lines: murine macrophages RAW 264.7 and chinese hamster ovary cells (CHOK1). At least in CHOK1 cells, DK107 has an impaired ability to evoke cholesterol mobilization from cholesteryl ester depots and recently synthesized pools. However both mutants have a normal activity to promote cholesterol efflux in both cellular lines. Using an specific antibody we have detected that DK107, but not DK226, increased acyl-CoA cholesterol acyl transferase (ACAT) protein level in both cell lines. We have assayed different cholesterol loading conditions in order to investigate their influence on ACAT expression.