FIGURE 3.

A model for heparan sulfate proteoglycan co-receptor function affecting autophagy, lipid metabolism and mitochondrial function. Growth factor signaling modulated by HSPGs affect signaling pathways that regulate mTOR activity. TOR is an inhibitor of autophagy and thus compromising mTOR activation promotes autophagy and downstream events, including lipophagy and mobilization of fatty acids from lipid droplets, mitochondrial fusion, and β-oxidation of lipids in mitochondria to generate ATP and lower intracellular lipid stores. Elements of this figure reflect events summarized in a published review (Hsu et al., 2021).