Long Chain Acyl-CoA Synthetase 3-mediated Phosphatidylcholine Synthesis Is Required for Assembly of Very Low Density Lipoproteins in Human Hepatoma Huh7 Cells

Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
Journal of Biological Chemistry (Impact Factor: 4.57). 02/2008; 283(2):849-54. DOI: 10.1074/jbc.M706160200
Source: PubMed


Hepatocytes play a crucial role in regulating lipid metabolism by exporting cholesterol and triglyceride into plasma through secretion of very low density lipoproteins (VLDL). VLDL production is also required for release of hepatitis C virus (HCV) from infected hepatocytes. Here, we show that long chain acyl-CoA synthetase 3 (ACSL3) plays a crucial role in secretion of VLDL and HCV from hepatocytes. In cultured human hepatoma Huh7 cells, ACSL3 is specifically required for incorporation of fatty acids into phosphatidylcholine. In cells receiving small interfering RNA targeting ACSL3, secretion of apolipoprotein B, the major protein component of VLDL, was inhibited and the lipoprotein was rapidly degraded. This inhibition in secretion was completely eliminated when these cells were treated with phosphatidylcholine. Treatment of cells with small interfering RNA targeting ACSL3 also inhibited secretion of HCV from Huh7-derived cells. These results identify ACSL3 as a new enzymatic target to limit VLDL secretion and HCV infection.

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    • "Among the different members of the ACSL family, member 3 and 6 have a strong preference for activation of long-chain fatty acids toward synthesis of the glycerophospholipid phosphatidylcholine [38], [39]. ACLS3 and ACSL6 are membrane proteins associated with different organelles, such as the ER and Golgi apparatus [24], [25]. "
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    ABSTRACT: Chlamydia trachomatis (Ct) is an obligate intracellular human pathogen that multiplies within a parasitophorous vacuole called an inclusion. We report that the location of several host-cell proteins present in the cytosol, the nucleus, and membranes was altered during Ct development. The acyl-CoA synthetase enzyme ACSL3 and the soluble acyl-CoA binding protein ACBD6 were mobilized from organelle membranes and the nucleus, respectively, into the lumen of the inclusion. The nuclear protein ZNF23, a pro-apoptosis factor, was also translocated into the inclusion lumen. ZNF23, among other proteins, might be targeted by Ct to inhibit host cell apoptosis, thereby enabling bacterial survival. In contrast, the acyl-CoA:lysophosphatidylcholine acyltransferase LPCAT1, an endoplasmic reticulum membrane protein, was recruited to the inclusion membrane. The coordinated action of ACBD6, ACSL3 and LPCAT1 likely supports remodeling and scavenging of host lipids into bacterial-specific moieties essential to Ct growth. To our knowledge, these are the first identified host proteins known to be intercepted and translocated into the inclusion.
    PLoS ONE 05/2012; 7(5):e36843. DOI:10.1371/journal.pone.0036843 · 3.23 Impact Factor
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    • "The importance of the PC biosynthetic pathway in HCV replication has been shown previously; one recent study demonstrated a progressive accumulation of several PC species during HCV infection [14]. In addition, Yao et al demonstrated that the enzyme, long chain acyl-CoA synthetase 3 (ACSL3), is specifically required for incorporation of fatty acids into phosphatidylcholine and treatment of cells with siRNA targeting ACSL3 inhibited the secretion of VLDL and HCV particles from hepatocytes [35]. PC synthesis is required for the normal secretion of VLDL by hepatocytes [27] and it has previously been suggested that HCV uses the VLDL assembly and secretion pathway for maturation and secretion of viral particles [10], [11]. "
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    PLoS ONE 08/2011; 6(8):e23641. DOI:10.1371/journal.pone.0023641 · 3.23 Impact Factor
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    • "The protein repertoire of CLDs included ACSL3 and ACSL4, which are responsible for the activation of fatty acids prior to their entry into metabolic pathways, such as de novo lipid synthesis, fatty acid catabolism or remodelling of membranes. In human Huh7 hepatocytes, ACSL activity has been involved in local synthesis of neutral lipids in lipid droplets (Fujimoto et al., 2007) and, more recently, ACSL3, which is the most abundant ACSL in Caco-2/TC7 enterocyte lipid droplet proteome, has been shown to be specifically required for fatty acid incorporation into PC, an essential reaction for VLDL (very-low-density lipoprotein) assembly, the hepatic form of TRL (Yao and Ye, 2008). Although major differences exist, it is interesting to note that the complex and highly differentiated function of TRL assembly and secretion is shared by hepatocytes and enterocytes. "
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    Biology of the Cell 07/2011; 103(11):499-517. DOI:10.1042/BC20110024 · 3.51 Impact Factor
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