Biology subjects

Domingo, I. K.

Publications and source records attributed to Domingo, I. K..

4 recordsLinked to original sources

bioRxiv2025

aPKC-ζ III promotes trophoblast fusion by altering Par-3 interactions with Hippo Signaling Kinase LATS1

The first trimester of pregnancy is a critical developmental period for the placenta. In humans, the maternal-facing exchange surface is formed by a single giant multinucleate syncytium: the syncytiotrophoblast (ST). The ST arises from villous lineage commitment of trophoblast stem cells (TSC) and the differentiation and fusion of progenitor cytotrophoblasts (pCT) to form the multinucleate syncytium. The Hippo signaling co-transcription factor YAP1 promotes pCT maintenance and TSC stemness, however, how Hippo signaling is regulated remains unknown. We have identified a novel PRKCZ encoded aPKC isoform, aPKC-{zeta} III, that is highly expressed in pCT and ST. Here we establish that aPKC-{zeta} III promotes pCT fusion by regulating Hippo signaling. Specifically, aPKC-{zeta} III outcompetes the Hippo kinase LATS1 for scaffolding protein Par-3 binding, resulting in YAP1 inactivation and pCT fusion. Our findings identify a key modulator of Hippo signaling in human trophoblasts that is critical for first trimester ST differentiation.

developmental biology↗

bioRxiv2024

Placental cytotrophoblast microvillar stabilization is required for cell-cell fusion

The placenta is an essential organ of pregnancy required for maternal-fetal transport and communication. The surface of the placenta facing the maternal blood is formed by a single giant multinucleate cell: the syncytiotrophoblast. The syncytiotrophoblast is formed and maintained via fusion of progenitor cytotrophoblasts. Cell-cell fusion is a tightly regulated process, and in non-trophoblastic cells is accompanied by stereotypical alterations in cell shape by cells that have attained fusion-competence. The most prominent feature is the formation of actin-based membrane protrusions, but whether stereotypic morphological changes occur in fusion-competent cytotrophoblasts has not been characterized. Using a human placental explant model, we characterized cell shape factors associated with the attainment of cytotrophoblast fusion competence. We found that fusion-competent cytotrophoblasts are hypertrophic, elongated cells, that form microvilli at the apical membrane. The actin-membrane cross linker protein ezrin was found to have highly polarized expression within cytotrophoblast microvilli. Inhibition of ezrin activation destabilized cytotrophoblast microvilli and prevented cytotrophoblast fusion. Thus, we propose that the polarized activation of ezrin within apical microvilli and actin-mediated changes in membrane dynamics are necessary for cytotrophoblast fusion. Summary statementFusion-competent cytotrophoblasts undergo dynamic changes in cell morphology including the acquisition of apically localized microvilli. Microvillar stabilization facilitates effective fusion and differentiation.

developmental biology↗

bioRxiv2022

Cisplatin toxicity is mediated by direct binding to TLR4 through a mechanism that is distinct from metal allergens

Cisplatin is an effective chemotherapeutic agent, yet its use is limited by several adverse drug reactions, known as cisplatin-induced toxicities (CITs). We recently demonstrated that cisplatin could elicit pro-inflammatory responses associated with CITs through Toll-like Receptor 4 (TLR4). TLR4 is best recognized for binding bacterial lipopolysaccharide (LPS) via its coreceptor, MD-2. TLR4 is also proposed to directly bind transition metals, such as nickel. Little is known about the nature of the cisplatin-TLR4 interaction. Here, we show that soluble TLR4 was capable of blocking cisplatin-induced, but not LPS-induced TLR4 activation. Cisplatin and nickel, but not LPS, were able to directly bind soluble TLR4 in a microscale thermophoresis binding assay. Interestingly, TLR4 histidine variants that abolish nickel binding, reduced, but did not eliminate, cisplatin-induced TLR4 activation. This was corroborated by binding data that showed cisplatin, but not nickel, could directly bind mouse TLR4 that lacks these histidine residues. Altogether, our findings suggest that TLR4 can directly bind cisplatin in a manner that is enhanced by, but not dependent on, histidine residues that facilitate binding to transition metals.

pharmacology and toxicology↗

bioRxiv2020

Toll-like receptor 4 is activated by platinum and contributes to cisplatin-induced ototoxicity

Toll-like receptor 4 (TLR4) is famous for recognizing the bacterial endotoxin lipopolysaccharide (LPS) as its canonical ligand. TLR4 is also activated by other classes of agonist including some Group 9/10 transition metals. Roles for these non-canonical ligands in pathobiology mostly remain obscure, though TLR4 interactions with metals can mediate immune hypersensitivity reactions. In this work, we tested whether TLR4 can be activated by the Group 10 transition metal, platinum. We demonstrated that in the presence of TLR4, platinum activates pathways downstream of TLR4 to a similar extent as the known TLR4 agonists LPS and nickel. Platinum is the active moiety in cisplatin, a very potent and invaluable chemotherapeutic used to treat solid tumors in childhood cancer patients. Unfortunately, cisplatin use is limited due to an adverse effect of permanent hearing loss (cisplatin-induced ototoxicity, CIO). Herein, we demonstrated that cisplatin also activates TLR4, prompting the hypothesis that TLR4 mediates aspects of CIO. Cisplatin activation of TLR4 was independent of the TLR4 co-receptors CD14 and MD-2, which is consistent with TLR4 signaling elicited by transition metals. We found that TLR4 is required for cisplatin-induced inflammatory, oxidative and apoptotic responses in an ear outer hair cell line and for hair cell damage in vivo. Thus, TLR4 is a promising therapeutic target to mitigate CIO. We additionally identify a TLR4 small molecule inhibitor able to curtail cisplatin toxicity in vitro. Further work is warranted towards inhibiting TLR4 as a route to mitigating this adverse outcome of childhood cancer treatment.Significance Statement This work identifies platinum, and its derivative cisplatin, as new agonists for TLR4. TLR4 contributes to cisplatin-induced hair cell death in vitro and in vivo. Genetic and small molecule inhibition of TLR4 identify this receptor as a druggable therapeutic target with promise to curtail cisplatin-induced ototoxicity, a devastating side-effect of an otherwise invaluable chemotherapeutic tool.Competing Interest StatementThe authors have declared no competing interest.View Full Text

pharmacology and toxicology↗