Cell surface heparan sulfate proteoglycans contribute to intracellular lipid accumulation in adipocytes

Larissa C Wilsie , Shree Chanchani , Deepti Navaratna and Robert A Orlando

Department of Biochemistry and Molecular Biology, University of New Mexico, Health Sciences Center, 915 Camino de Salud, Albuquerque, New Mexico, 87131, USA

author email corresponding author email

Lipids in Health and Disease 2005, 4:2doi:10.1186/1476-511X-4-2


Published:	6 January 2005

Abstract

Background

Transport of fatty acids within the cytosol of adipocytes and their subsequent assimilation into lipid droplets has been thoroughly investigated; however, the mechanism by which fatty acids are transported across the plasma membrane from the extracellular environment remains unclear. Since triacylglycerol-rich lipoproteins represent an abundant source of fatty acids for adipocyte utilization, we have investigated the expression levels of cell surface lipoprotein receptors and their functional contributions toward intracellular lipid accumulation; these include very low density lipoprotein receptor (VLDL-R), low density lipoprotein receptor-related protein (LRP), and heparan sulfate proteoglycans (HSPG).

Results

We found that expression of these three lipoprotein receptors increased 5-fold, 2-fold, and 2.5-fold, respectively, during adipocyte differentiation. The major proteoglycans expressed by mature adipocytes are of high molecular weight (>500 kD) and contain both heparan and chondroitin sulfate moieties. Using ligand binding antagonists, we observed that HSPG, rather than VLDL-R or LRP, play a primary role in the uptake of DiI-lableled apoE-VLDL by mature adipocytes. In addition, inhibitors of HSPG maturation resulted in a significant reduction (>85%) in intracellular lipid accumulation.

Conclusions

These results suggest that cell surface HSPG is required for fatty acid transport across the plasma membrane of adipocytes.