The Toxoplasma gondii inhibitor-2 regulates protein phosphatase 1 activity through multiple motifs

Abstract

Toxoplasma gondii has a complex life cycle characterized by multiple differentiation steps that are essential for its survival in both human and definitive feline host. Several studies have demonstrated the importance of phosphorylations by protein kinases during the life cycle of T. gondii. However, very little is known about protein phosphatases and their regulators in the parasite. We report the molecular and functional characterization of the T. gondii ortholog of the inhibitor-2 protein, designated TgI2. We show that TgI2 encompasses conserved motifs involved in the interaction and modulation of the phosphatase activity of T. gondii protein phosphatase 1, named TgPP1. We show that a specific combination of motifs is involved in binding and/or inhibition of the TgPP1 activity. We show here that the TgI2 protein is a potent inhibitor of TgPP1 phosphatase activity. TgI2 SILK and RVxF motifs are critical for regulating the activity of TgPP1, a feature that is common with the higher eukaryotes inhibitor-2 protein.

PP2Acα-B′/PR61 Holoenzyme of Toxoplasma gondii Is Required for the Amylopectin Metabolism and Proliferation of Tachyzoites

“…Neither amylopectin granules nor polysaccharides were detected in the control tachyzoites, and the accumulation of amylopectin in the OA-treated groups did not multiply with the increase of the OA treatment concentration. Considering the specific potencies of OA to inhibit both PP1 and PP2A in mammalian cells ( 17 ) and the previous report that 50 nM OA did not obviously inhibit recombinant Tg PP1 ( 18 ), our results indicate that the PP2A subfamily plays a role in the metabolism of polysaccharides of T. gondii tachyzoites.…”

Deciphering the Role of Protein Phosphatases in Apicomplexa: The Future of Innovative Therapeutics?

“…Furthermore, the micro-injection of oocytes with cRNA of Tg LRR1 led to nearly a total germinal vesicle breakdown of oocytes, suggesting that Tg LRR1 can inhibit the Xenopus PP1. A more recent study regarding inhibitors of Tg PP1characterized inhibitor-2 ( Tg I2) that it functions similarly to its eukaryotic homologs exhibiting inhibitory activity [ 103 ]. The Tg I2 inhibitor has three different motifs (SILK-like, RVxF, and FKK/HYNE).…”

“…The Tg I2 inhibitor has three different motifs (SILK-like, RVxF, and FKK/HYNE). Tg PP1 associates with Tg I2 through the RVxF motif, whereas other motifs play a more minor role in the binding to Tg PP1 [ 103 ]. However, both SILK-like and RVxF motifs are critical for regulating the activity of Tg PP1, a feature that is common with the higher eukaryote’s Inhibitor-2 protein but was not observed for Pf PP1 [ 103 ].…”

“…Tg PP1 associates with Tg I2 through the RVxF motif, whereas other motifs play a more minor role in the binding to Tg PP1 [ 103 ]. However, both SILK-like and RVxF motifs are critical for regulating the activity of Tg PP1, a feature that is common with the higher eukaryote’s Inhibitor-2 protein but was not observed for Pf PP1 [ 103 ]. Relatively little has been described regarding Tg PP1 biological function.…”

Structural and Functional Insights into the Microtubule Organizing Centers of <em>Toxoplasma gondii</em> and <em>Plasmodium spp</em>.

“…TgI2 was shown to inhibit TgPP1's phosphatase activity in vitro. This inhibition is critically dependent on TgI2's SILK and RVxF motifs, a feature conserved in the higher eukaryotes I-2s (Deveuve et al, 2017). In addition, A leucine-rich repeat protein family, TgLRR1, binds TgPP1 within the nucleus.…”