Antiretroviral therapy-naive people living with HIV possess less fat than people without HIV. Previously, we found that HIV-1 transactivator of transcription (TAT) decreases fat in ob/ob mice. The TAT38 (a.a. 20-57) is important in the inhibition of adipogenesis and contains three functional domains: Cys-ZF domain (a.a. 20-35 TACTNCYCAKCCFQVC), core-domain (a.a. 36-46, FITKALGISYG), and protein transduction domain (PTD)(a.a. 47-57, RAKRRQRRR). Interestingly, the TAT38 region interacts with the Cyclin T1 of the P-TEFb complex, of which expression increases during adipogenesis. The X-ray crystallographic structure of the complex showed that the Cys-ZF and the core domain bind to the Cyclin T1 via hydrophobic interactions. To prepare TAT38 mimics with structural and functional similarities to TAT38, we replaced the core domain with a hydrophobic aliphatic amino acid (from carbon numbers 5 to 8). The TAT38 mimics with 6-hexanoic amino acid (TAT38 Ahx (C6)) and 7-heptanoic amino acid (TAT38 Ahp (C7)) inhibited adipogenesis of 3T3-L1 potently, reduced cellular triglyceride content, and decreased body weight of diet-induced obese (DIO) mice by 10.4-11 % in two weeks. The TAT38 and the TAT38 mimics potently repressed the adipogenic transcription factors genes, C/EBPα, PPARγ, and SREBP1. Also, they inhibit the phosphorylation of PPARγ. The TAT peptides may be promising candidates for development into a drug against obesity or diabetes.
Keywords: Adipogenesis; C/EBPα (CAAT enhancer binding protein alpha); CDK9 (cyclin-dependent kinase 9); CyclinT1; PPARγ; TAT (transcription activator of transcription of HIV-1).
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