Human FABP1 T94A variant enhances cholesterol uptake

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• The human liver fatty acid binding protein (FABP1) T94A variant is known to affect serum lipoprotein cholesterol levels.
• The precise mechanisms by which this FABP1 variant influences cholesterol metabolism remain unclear.

Purpose of the Study:

• To investigate the in vitro cholesterol-binding properties of the FABP1 T94A variant compared to wild-type (WT) FABP1.
• To examine the impact of the FABP1 T94A variant on cholesterol uptake in primary human hepatocytes.

Main Methods:

• Purified recombinant WT (T94T) and T94A variant FABP1 proteins were used for in vitro cholesterol binding assays.
• NBD-cholesterol fluorescence binding assays and isothermal titration microcalorimetry (ITC) were employed to quantify binding affinity.
• Primary human hepatocytes genotyped as TT (WT) or CC (T94A variant) were used to assess cholesterol uptake and FABP1 protein levels.

Main Results:

• The FABP1 T94A variant exhibited a 3-fold higher affinity for cholesterol binding compared to WT FABP1.
• Hepatocytes expressing the T94A variant (CC genotype) showed 30% higher total FABP1 protein levels.
• Cholesterol uptake mediated by HDL and LDL was significantly faster in CC variant hepatocytes than in WT TT hepatocytes.
• VLDL-mediated cholesterol uptake did not differ between the genotypes, and mRNA levels of key lipoprotein-related genes remained unchanged.

Conclusions:

• The increased cholesterol-binding affinity of the FABP1 T94A variant protein and/or elevated total protein levels contribute to enhanced HDL- and LDL-mediated cholesterol uptake in hepatocytes.
• These findings provide a molecular basis for how the FABP1 T94A variant influences lipoprotein cholesterol metabolism.