所属 埼玉医科大学 医学部 国際医療センター 皮膚科（皮膚腫瘍科） 職種 助教
|Cholesterol loading in macrophages stimulates formation of ER-derived vesicles with elevated ACAT1 activity
|正式名：JOURNAL OF LIPID RESEARCH
|AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
|Naomi Sakashita,Catherine C. Y. Chang,Xiaofeng Lei,Yukio Fujiwara,Motohiro Takeya,Ta-Yuan Chang
|ACAT1 is normally a resident enzyme in the endoplasmic reticulum (ER). We previously showed that treating macrophages with denatured LDL causes a large increase in ER-derived, ACAT1-positive vesicles. Here, we isolated ER membranes and ER-derived vesicles to examine their ACAT enzyme activity in vitro. The results showed that when macrophages are grown under normal conditions, ACAT1 is located in high density ER membrane; its enzymatic activity is relatively low. Loading macrophages with cholesterol did not increase the total cellular ACAT1 protein content significantly but caused more ACAT1 to appear in ER-derived vesicles. These vesicles exhibit lower density and are associated with markers of both ER and the trans-Golgi network. When normalized with equal ACAT1 protein mass, the enzymatic activities of ACAT1 in ER-derived vesicles were 3-fold higher than those present in ER membrane. Results using reconstituted ACAT enzyme assay showed that the increase in enzyme activity in ER-derived vesicles is not due to an increase in the cholesterol content associated with these vesicles. Overall, our results show that macrophages cope with cholesterol loading by using a novel mechanism: they produce more ER-derived vesicles with elevated ACAT1 enzyme activity without having to produce more ACAT1 protein.-Sakashita, N., C. C. Y. Chang, X. Lei, Y. Fujiwara, M. Takeya, and T-Y. Chang. Cholesterol loading in macrophages stimulates formation of ER-derived vesicles with elevated ACAT1 activity. J. Lipid Res. 2010. 51: 1263-1272.