Abstract
The Acyl-CoA-binding domain-containing protein (ACBD3) plays multiple roles across the cell. Although generally associated with the Golgi apparatus, it operates also in mitochondria. In steroidogenic cells, ACBD3 is an important part of a multiprotein complex transporting cholesterol into mitochondria. Balance in mitochondrial cholesterol is essential for proper mitochondrial protein biosynthesis, among others. We generated ACBD3 knock-out (ACBD3-KO) HEK293 and HeLa cells and characterized the impact of protein absence on mitochondria, Golgi, and lipid profile. In ACBD3-KO cells, cholesterol level and mitochondrial structure and functions are not altered, demonstrating that an alternative pathway of cholesterol transport into mitochondria exists. However, ACBD3-KO cells exhibit enlarged Golgi area with absence of stacks and ribbon-like formation, confirming the importance of ACBD3 in Golgi stacking. The glycosylation of the LAMP2 glycoprotein was not affected by the altered Golgi structure. Moreover, decreased sphingomyelins together with normal ceramides and sphingomyelin synthase activity reveal the importance of ACBD3 in ceramide transport from ER to Golgi.
Highlights
Humans express seven highly conserved Acyl-CoA-binding proteins (ACBD1–ACBD7).A common feature of this protein family is the ACB domain, responsible for the binding of long-chain fatty Acyl-CoA esters
Of the ACBD3 signal compared to the cell lysate and insignificant contamination of cytosol (β-actin), but the mitochondrial fraction showed an enrichment by ER, in addition to a faint signal of the Golgi protein GM-130 (Figure 1A)
15% of the ACBD3 signal compared to the cell lysate and insignificant contamination cytosol (β-actin), but the mitochondrial fraction showed an enrichment by ER, in addit to a faint signal of the Golgi protein GM-130 (Figure 1A)
Summary
Humans express seven highly conserved Acyl-CoA-binding proteins (ACBD1–ACBD7). A common feature of this protein family is the ACB domain, responsible for the binding of long-chain fatty Acyl-CoA esters. ACBD3 is the largest protein of this family, consisting, apart from the ACB domain, of a coiled-coil domain in the middle and a Golgi dynamics (GOLD) domain on the C terminus. The GOLD domain is responsible for multiple protein interactions and may be used to stabilize peripheral membrane proteins at intracellular membranes. As reported in The Human Protein Atlas [1], ACBD3 is highly expressed in some organs of the digestive system, brain, prostate, placenta, and bone marrow; medium expression is characteristic of male and female reproductive tissues (for a complete summary, see Table A1). According to its antibody validation profile, ACBD3 is localized in
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