Iron triggers
Tv
PI4P5K proteostasis and Arf-mediated cell membrane trafficking to regulate PIP
2
signaling crucial for multiple pathogenic activities of the parasitic protozoan
Trichomonas vaginalis
Authors: Wu Kuan-Yi , Chen Yen-Ju , Lin Shu-Fan , Hsu Hong-Ming 
Published: December 2024

Trichomonas vaginalis
is the etiologic agent of trichomoniasis, one of the most common non-viral sexually transmitted infections globally. Our previous work reported the role of phosphatidylinositol 4,5-bisphosphates (PIP
2
) signaling in the actin-dependent pathogenicity of
T. vaginalis
. This study further demonstrated that iron transiently regulated
T. vaginalis
phosphatidylinositol-4-phosphate 5-kinase (
Tv
PI4P5K) proteostasis and its complex formation with an active ADP ribosylation factor
Tv
Arf220, facilitating co-trafficking to the plasma membrane, crucial for PIP
2
production. In dominant-active HA-
Tv
Arf220 Q71L mutant,
Tv
PI4P5K plasma membrane trafficking, PIP
2
production, and intracellular calcium levels were increased, while these processes were inhibited in dominant-negative T31N mutant or those by Brefeldin A (BFA) treatment. Additionally, PIP
2
replenishment reversed these inhibitions in the T31N mutant, suggesting the critical role of
Tv
Arf220 activation in PIP
2
-calcium signaling. Also, T31N mutant and BFA treatment impaired actin dynamics and cytoskeleton-dependent processes in
T. vaginalis
, further linking the role of
Tv
Arf220 to PIP
2
-calcium-dependent actin dynamics. Beyond cytoadherence, during host-parasite interactions,
Tv
Arf220 influenced both contact-dependent and -independent cytotoxicity, as well as phagocytotic capacity, contributing to the cytopathogenesis of human vaginal epithelial cells. Our findings underscore the key upstream regulation mechanisms of the PIP
2
signaling, orchestrating the interplay between
Tv
Arf220-PIP
2
-calcium signaling and downstream actin cytoskeleton-driven pathogenicity in
T. vaginalis
.

IMPORTANCE

Trichomonas vaginalis
actin cytoskeleton-centric pathogenicity is regulated by the phosphatidylinositol 4,5-bisphosphates (PIP
2
)-triggered calcium signaling cascade in response to environmental iron, though the detailed mechanism by which iron modulates PIP
2
signaling remains unclear. Our findings reveal that iron rapidly induces
T. vaginalis
phosphatidylinositol-4-phosphate 5-kinase (
Tv
PI4P5K) translation followed by its degradation, while simultaneously activating
Tv
Arf220 binding, which facilitates
Tv
PI4P5K localization to the plasma membrane for PIP
2
production. In contrast to the
Tv
Arf220 Q71L mutant, the reduced PIP
2
production, intracellular calcium, actin assembly, morphogenesis, and cytoadherence in the dominant-negative T31N mutant were recovered by PIP
2
supplementation, indicating the essential role of
Tv
Arf220 in PIP
2
-dependent calcium signaling. Additionally, the contact-dependent or -independent cytotoxicity, along with the phagocytosis, was impaired in the
Tv
PI4P5K- or
Tv
Arf220-deficient parasites, as well as in those treated with BAPTA or Latrunculin B. These findings highlight that
Tv
Arf220-mediated PIP
2
-calcium signaling cascade regulates actin cytoskeleton and cytopathogenicity of
T. vaginalis
. This study uncovers a novel pathogenic mechanism and suggests potential therapeutic targets for parasite control.