Multilevel Approach for the Treatment of Giardiasis by Targeting Arginine Deiminase

Giardiasis represents a latent problem in public health due to the exceptionally pathogenic strategies of the parasite Giardia lamblia for evading the human immune system. Strains resistant to first-line drugs are also a challenge. Therefore, new antigiardial therapies are urgently needed. Here, we tested giardial arginine deiminase (GlADI) as a target against giardiasis. GlADI belongs to an essential pathway in Giardia for the synthesis of ATP, which is absent in humans. In silico docking with six thiol-reactive compounds was performed; four of which are approved drugs for humans. Recombinant GlADI was used in enzyme inhibition assays, and computational in silico predictions and spectroscopic studies were applied to follow the enzyme's structural disturbance and identify possible effective drugs. Inhibition by modification of cysteines was corroborated using Ellman's method. The efficacy of these drugs on parasite viability was assayed on Giardia trophozoites, along with the inhibition of the endogenous GlADI. The most potent drug against GlADI was assayed on Giardia encystment. The tested drugs inhibited the recombinant GlADI by modifying its cysteines and, potentially, by altering its 3D structure. Only rabeprazole and omeprazole decreased trophozoite survival by inhibiting endogenous GlADI, while rabeprazole also decreased the Giardia encystment rate. These findings demonstrate the potential of GlADI as a target against giardiasis.

Lineage Specification from Prostate Progenitor Cells Requires Gata3-Dependent Mitotic Spindle Orientation

During prostate development, basal and luminal cell lineages are generated through symmetric and asymmetric divisions of bipotent basal cells. However, the extent to which spindle orientation controls division symmetry or cell fate, and the upstream factors regulating this process, are still elusive. We report that GATA3 is expressed in both prostate basal progenitor and luminal cells and that loss of GATA3 leads to a mislocalization of PRKCZ, resulting in mitotic spindle randomization during progenitor cell division. Inherently proliferative intermediate progenitor cells accumulate, leading to an expansion of the luminal compartment. These defects ultimately result in a loss of tissue polarity and defective branching morphogenesis. We further show that disrupting the interaction between PRKCZ and PARD6B is sufficient to recapitulate the spindle and cell lineage phenotypes. Collectively, these results identify a critical role for GATA3 in prostate lineage specification, and further highlight the importance of regulating spindle orientation for hierarchical cell lineage organization.

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Gata3 regulates prostate lineage specification and tissue architecture

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Loss of Gata3 causes aPKC mislocalization and mitotic spindle randomization

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aPKC-Par6 decoupling randomizes the spindle and perturbs lineage specification

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Spindle regulation prevents progenitor cell accumulation and tissue hyperplasia

A small molecule inhibitor of atypical protein kinase C signaling inhibits pancreatic cancer cell transformed growth and invasion

Pancreatic cancer is highly resistant to current chemotherapies. Identification of the critical signaling pathways that mediate pancreatic cancer transformed growth is necessary for the development of more effective therapeutic treatments. Recently, we demonstrated that protein kinase C iota (PKCι) and zeta (PKCζ) promote pancreatic cancer transformed growth and invasion, by activating Rac1→ERK and STAT3 signaling pathways, respectively. However, a key question is whether PKCι and PKCζ play redundant (or non-redundant) roles in pancreatic cancer cell transformed growth. Here we describe the novel observations that 1) PKCι and PKCζ are non-redundant in the context of the transformed growth of pancreatic cancer cells; 2) a gold-containing small molecule known to disrupt the PKCι/Par6 interaction, aurothiomalate, also disrupts PKCζ/Par6 interaction; 3) aurothiomalate inhibits downstream signaling of both PKCι and PKCζ, and blocks transformed growth of pancreatic cancer cells in vitro; and 4) aurothiomalate inhibits pancreatic cancer tumor growth and metastasis in vivo. Taken together, these data provide convincing evidence that an inhibitor of atypical PKC signaling inhibits two key oncogenic signaling pathways, driven non-redundantly by PKCι and PKCζ, to significantly reduce tumor growth and metastasis. Our results demonstrate that inhibition of atypical PKC signaling is a promising therapeutic strategy to treat pancreatic cancer.