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. Author manuscript; available in PMC: 2019 Mar 25.
Published in final edited form as: Matrix Biol. 2018 May 24;71-72:262–282. doi: 10.1016/j.matbio.2018.05.010

FIGURE 2. The role of HSPGs in LPL metabolism.

FIGURE 2.

Lipoprotein lipase (LPL) is synthesized by parenchymal cells including myocytes, macrophage cardiomyocytes and adipocytes. After being processed in the Golgi mature LPL is secreted into the interstitial spaces. Once secreted, LPL is initially captured by cell surface HSPGs and transferred to the interstitial HSPG, COL18 (dashed arrow). Bound LPL is then transferred to GPIHBP1 on the basolateral surface of capillary endothelial cells. GPIHBP1 binding stabilizes LPL activity and allows the transendothelial transport of the LPL-GPIHBP1 complex to the lumenal side of the endothelium. In the capillary lumen, the LPL-GPIHBP1 complex facilitates TRL margination in regions of the endothelium devoid of HSPGs. The TRL-LPL-GPIHBP1 interaction allows LPL-mediated triglyceride hydrolysis to occur. TRLs reach a critical size thereby limiting the interaction with the LPL-GPIHBP1 complex and resulting in the release of TLR remnants into the circulation. LPL, Lipoprotein Lipase; COL18, Collagen XVIII; GPIHBP1, glycosylphosphatidylinositol anchored high-density lipoprotein binding protein 1.