Calcineurin-binding peptide VIVIT inhibits Ca⁺⁺-dependent induction of KSHV lytic protein expression.

BCBL-1 cells were retrovirally transduced with EGFP or EGFP-VIVIT fusion protein (see “Materials and methods”). Then cells were incubated with ionomycin (1 μg/mL) or TPA (15 nM). After 3 days, cells were labeled with Dead Red, fixed, permeabilized, and labeled with anti–PF-8 or anti-gpK8.1 mAbs followed by PE-conjugated secondary antibodies. Green fluorescent viable cells were gated and examined for the expression of KSHV lytic proteins. Expression of PF-8 after induction by ionomycin in EGFP- (A) or EGFP-VIVIT–transduced (B) cells. (C) Isotype control for ionomycin-induced EGFP-VIVIT cells. The number of cells within the defined region reflects the percentage of PF-8–positive cells. Ionomycin or TPA induction of PF-8– (D) or gpK8.1-positive (E) cells in EGFP-VIVIT– (▧) and EGFP-transduced (■) cells compared to concurrent induction in nontransduced cells (▪). Data represent mean ± SEM of 4 separate experiments. *P < .01 compared to induction by ionomycin in EGFP-transduced or nontransduced cells.