Participation of SCP2 in cholesterol utilization

Gavey et al. [22] studied the participation of SCP2 in the conversion of cholesterol to cholesterol ester (acyl-CoA cholesterol acyl transferase, ACAT) by rat liver microsomes. The effect of rat liver cytosol on the conversion of [4- Cjcholesterol to cholesterol ester was examined as a function of cytosol protein added. In the absence of cytosol, microsomes formed 1.0 nmole of labeled cholesterol ester/mg microsomal protein/2 h. The addition of rat liver cytosol to the microsomes produced a marked, concentration-dependent, increase in the amount of exogenously added [4- C]cholesterol that was converted to cholesterol ester. Specifically, with the addition of 37.6 mg of cytosol to the microsomes, 12.9 nmoles of labeled cholesterol ester/mg microsomal protein/2 h were formed. When cytosol was incubated with [4- C]cholesteroI in the absence of microsomes, no cholesterol esters were formed. 

These results demonstrate that SCP2 participates in the microsomal conversion of cholesterol to cholesterol ester. It is quite possible that SCP2 participates in the delivery of either exogenous (dietary) or endogenous (microsomally bound) cholesterol to ACAT which is bound to the endoplasmic reticulum. 

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