FIGURE 7.

Sterol-mediated lipin 1 expression modulates triglyceride accumulation through its PAP1 activity in Huh7 cells. A, Huh7 cells were cultured in medium containing sterols, LPDS, or statin for 24 h. Cell extracts were fractionated using the Qiagen Qproteome cell compartment kit, and aliquots (30 μg of protein/lane) were subjected to SDS-PAGE. Immunoblots were probed with anti-lipin-1 antibody. The experiments were repeated three times. B, Huh7 cells were cultured in medium containing sterols, LPDS, or statin for 48 h. PAP1 activity was measured using the cytosolic fraction, as described under “Experimental Procedures.” The statistical significance of statin versus sterols is indicated by asterisks (**, p < 0.01). Values represent means ± S.E. (n = 3). C, Huh7 cells were transfected with 25 nm control siRNA, LPIN1 siRNA 1 (siRNA#1), or LPIN1 siRNA 2 (siRNA#2). Forty-eight hours after transfection, the cells were cultured in medium containing sterols or statin. After incubation for 48 h, cell extracts were prepared, and aliquots (50 μg of protein/lane) were subjected to SDS-PAGE. Immunoblots were probed with anti-lipin-1 antibody or anti-lamin B2 antibody. The experiments were repeated three times. D, Huh7 cells were transfected with each siRNA and cultured in medium containing sterols or statin for 72 h, as in C. The cellular TG content was measured and normalized to the total protein content. The statistical significance of statin versus sterols is indicated by asterisks (**, p < 0.01). N.S., not significant.