Cold-inducible Zfp516 activates UCP1 transcription to promote browning of white fat and development of brown fat

Abstract

Uncoupling protein 1 (UCP1) mediates nonshivering thermogenesis and, upon cold exposure, is induced in brown adipose tissue (BAT) and subcutaneous white adipose tissue (iWAT). Here, by high-throughput screening using the UCP1 promoter, we identify Zfp516 as a transcriptional activator of UCP1 as well as PGC1α, thereby promoting a BAT program. Zfp516 itself is induced by cold and sympathetic stimulation through the cAMP-CREB/ATF2 pathway. Zfp516 directly binds to the proximal region of the UCP1 promoter, not to the enhancer region where other transcription factors bind, and interacts with PRDM16 to activate the UCP1 promoter. Although ablation of Zfp516 causes embryonic lethality, knockout embryos still show drastically reduced BAT mass. Overexpression of Zfp516 in adipose tissue promotes browning of iWAT even at room temperature, increasing body temperature and energy expenditure and preventing diet-induced obesity. Zfp516 may represent a future target for obesity therapeutics.

Figure 1. Zfp516 is a Brown Fat- Enriched Transcription Factor that binds and activates UCP1 promoter

A. Top, diagram of Zfp516 structure. Bottom, immunoblotting for Zfp516, lamin (nuclear), and GAPDH (cytosolic) in nuclear and cytosolic fractions of HIB-1B cells. B. Top, GFP fluorescence of 293FT cells transfected with −5.5kb UCP1-GFP and either empty vector (EV) or Zfp516. Bottom, relative luciferase activity of 293FT cells cotransfected with −5.5kb UCP1-Luc and the indicated expression vector. C. Top and inlay, RT-qPCR and immunoblotting for Zfp516 mRNA and protein levels in BAT and WAT tissues from 6 week-old C57BL/6 mice (n=4 mice). Bottom, RT-qPCR for Zfp516 and UCP1 mRNA levels in the adipocyte fraction and SVF from BAT. D. Schematic representation of 5’ deletion constructs of the UCP1 promoter-luciferase and relative luciferase activity in 293FT cells cotransfected with indicated promoter construct and Zfp516 (expressed as fold of vector control). E. Top, ChIP for Zfp516 association to the UCP1 promoter in BAT. Bottom, qPCR for the ChIP DNA for Zfp516 association to the UCP1 promoter in BAT. F. Top-left, immunoblotting of lysates from 293FT cells transfected with −5.5kb UCP1-GFP with Flag-Zfp516 or vector. Top-right, ChIP for Flag-Zfp516 association to the UCP1 promoter using both αFlag and αZfp516 antibodies. Bottom, qPCR quantification of ChIP DNA for the association of full length Zfp516 or truncations of Zfp516 to the UCP1 promoter in 293FT cells. See also Figure S1, S2, and S3. *p<0.05; **p<0.01; ***p<0.001

Figure 2. Zfp516 directly interacts with PRDM16

A. Top-left (left column), immunoblot for various brown fat specific transcription factors after IP with αZfp516 antibody in 293FT cells cotransfected with Zfp516 and the indicated TF. Top-left (right side), immunoblot for Zfp516 protein after IP with αPRDM16 of lysates coexpressing Zfp516 and PRDM16. Top-right, immunoblot with αV5 or αFlag after IP with either Flag or V5 respectively of 293FT lysates transfected the indicated vectors. Bottom-left, immunoblot for either Zfp516 or PRDM16 after IP with indicated antibody of 50µg of BAT nuclear extracts. Bottom-right, Autoradiograph of GST pulldown using GST fusion proteins containing the indicated domains of PRDM16 and ³⁵S-labelled in vitro translated Zfp516. B. Left, luciferase activity of 293FT cells cotransfected with the −5.5kb UCP1 promoter with Zfp516 and PRDM16 either together or separately. Right, luciferase activity of 293 FT cells cotransfected with the −2.4kb PGC1α promoter with Zfp516 and PRDM16 either together or separately. *p<0.05; **p<0.01; ***p<0.001

Figure 3. Zfp516 is regulated by Cold through CREB/ATF

A. Top-left, RT-qPCR for selected genes in HIB-1B cells with or without 4h treatment with 10µM isoproterenol. Top-right, RT-qPCR for Zfp516, UCP1, and PGC1α mRNA in HIB-1B cells during 500µM IBMX treatment. Bottom, immunoblotting for Zfp516 or tubulin in HIB-1B cells treated with vehicle or indicated compound for 12h. Values are normalized to nontreated cells. B. Relative luciferase activity of 293FT cells transfected with the −2.0kb Zfp516-Luc and indicated transcription factor expression vector. C. RT-qPCR for Zfp516 and UCP1 mRNA in various tissues of wild-type mice following 10d of intraperitoneal injection with either CL316,243 or saline. D. RT-qPCR for Zfp516 and UCP1 mRNA (left and center) and immunoblotting for indicated proteins (right) in various adipose depots of wild-type mice exposed to cold (4°C) for 6h. See also Figure S4. *p<0.05; **p<0.01; ***p<0.001

Figure 4. Zfp516 Promotes Browning of White Adipose Tissue

A. Left, immunoblotting for Zfp516 in adipose depots of WT and aP2-Zfp516 mice (TG) with different transgene copy number. Right, RT-qPCR for Zfp516. B. Top, immunoblotting for UCP1 in adipose depots of WT and TG mice. Bottom, immunostaining for UCP1 in sections of iWAT and pWAT from WT and TG mice. C. Left, microarray analysis from iWAT of WT or TG mice. Right, RT-qPCR of genes from microarray in WT or TG mice (n= 3 per group). D. VO₂ assayed by indirect calorimetry in WT and TG mice on chow diet (CD) (n=6 mice per group). E. Oxygen consumption rate of iWAT from WT or TG mice. F. Rectal temperature measured in 15wk old WT and TG mice fed CD at room temperature (left) and after 4 h cold exposure (right) (n=7–8 mice per group). G. Left, representative photograph of 26wk old WT or TG mice fed HFD for 16wk. Center, body mass gain for the mice from left. Inlay, body weight in WT and TG mice fed HFD starting at 6wk old (n=6–8 mice per group). Right, mass of each adipose tissue depot and liver represented in percentage of body weight in the mice mentioned above. See also Figure S5. *p<0.05; **p<0.01; ***p<0.001

Figure 5. Zfp516 ablation blocks brown fat development in mice

A. Left, E20.5 WT and Zfp516 KO embryos from back view. White dots delineate area of BAT or presumptive BAT. Right, cropped image from left. B. Top, immunostaining for UCP1 in BAT or presumptive BAT in WT and KO embryos. Top middle, H&E staining of the BAT/WAT border in WT and KO mice. Bottom middle, ORO staining of WT or KO BAT. Bottom, transmission electron microscopy of WT and KO BAT mitochondria. C. Microarray analysis from BAT or presumptive BAT of WT or KO E20.5 embryos. D. RT-qPCR for BAT enriched (left) and muscle (right) genes in BAT from E17.5 WT or KO embryos (n=3). See also Figure S6. *p<0.05; **p<0.01; ***p<0.001.

Figure 6. Zfp516 promotes brown adipogenesis and suppresses myogenesis

A. Top, immunoblotting for indicated proteins (left), ORO staining (center) and RT-qPCR for BAT enriched genes and PPARγ (right) in C2C12 cells transduced with either GFP or Zfp516 adenovirus after 6 days of brown adipogenic differentiation. Bottom, Brightfield view at 20X (top left) and 40X (bottom left) magnification, RT-qPCR for Zfp516 mRNA (center), and RT-qPCR for muscle specific genes (right) in C2C12 cells transduced with GFP or Zfp516 adenovirus after 6d of myogenic differentiation. B. Top, RT-qPCR for Zfp516 mRNA (left), ORO staining and brightfield view pictures (center left), immunoblotting for indicated proteins (center right) and RT-qPCR for BAT enriched genes (right) in WT and KO MEFs after 5d of adipogenic differentiation. Bottom, RT-qPCR for Zfp516 mRNA (left), ORO staining and brightfield view pictures (center left), immunoblotting for indicated proteins (center right) and RT-qPCR for BAT enriched genes (right) in KO MEFs infected with GFP or Zfp516 adenovirus after 5d of adipogenic differentiation. C. Top-left, immunoblotting for indicated proteins in HIB-1B cells infected with control or sh-Zfp516 lentivirus after 5d of adipogenic differentiation. Top-right, ORO staining at day 5 of differentiation. Middle, RT-qPCR for mRNA level of Zfp516 and BAT enriched genes these cells. Bottom-left, RT-qPCR for mRNA level of common adipogenic genes. Bottom-right, Relative OCR rates in cells before and after oligomycin treatment. OCR measurements before drug injection in the control cells were set as 100%. (N=9–10). D. Top-left, Immunoblotting for indicated proteins in sh-Zfp516 HIB-1B cells or sh-Zfp516 infected with Zfp516 adenovirus after 5 days of adipogenic differentiation. Top-right, ORO staining at day 5 of differentiation. Middle, RT-qPCR for BAT enriched genes. Bottom, RT-qPCR for common adipogenic genes *p<0.05; **p<0.01; ***p<0.001.