EphA7 is required for otic epithelial homeostasis by modulating Claudin6 in Xenopus

RTP4 Enhances Corneal HSV-1 Infection in Mice With Type 2 Diabetes Mellitus

Purpose

The purpose of this study was to investigate whether corneal lesions in mice with type 2 diabetes mellitus (T2D) infected with herpes simplex virus (HSV)-1 are more severe, and to elucidate the specific underlying mechanism.

Methods

The corneas of control mice and T2D mice induced by a high-fat diet combined with streptozotocin were infected with the HSV-1 Mckrae strain to assess corneal infection, opacity, and HSV-1 replication. RNA sequencing of the corneal epithelium from wild-type and db/db mice (a genetic T2D mouse model) was conducted to identify the key gene affecting T2D infection. Immunofluorescence staining was performed on corneal sections from T2D mice and patients with T2D. The effect of small interfering RNA (siRNA) knockdown on corneal HSV-1 infection was evaluated in both in vitro and in vivo models.

Results

T2D mice exhibited a more severe infection phenotype following HSV-1 infection, characterized by augmented corneal opacity scores, elevated viral titers, and transcripts compared to control mice. Transcriptome analysis of corneal epithelium revealed a hyperactive viral response in T2D mice, highlighting the differentially expressed gene Rtp4 (encoding receptor transporter protein 4). Receptor transporter protein 4 (RTP4) expression was enhanced in the corneal epithelium of T2D mice and patients with T2D. Virus binding assays demonstrated that RTP4 facilitated HSV-1 binding to human corneal epithelial cells. Silencing RTP4 alleviated HSV-1 infection in both in vitro and in vivo T2D models.

Conclusions

The findings indicate that elevated RTP4 exacerbates HSV-1 infection by enhancing its binding to corneal epithelial cells, whereas Rtp4 knockdown mitigated corneal lesions in T2D mice. This implies RTP4 as a potential target for intervention in diabetic HSV-1 infection.

The role of tissue maturity and mechanical state in controlling cell extrusion

Epithelia remove dying or excess cells by extrusion, a process that seamlessly squeezes cells out of the layer without disrupting their barrier function. New studies shed light into the intricate relationship between extrusion, tissue mechanics, and development. They emphasize the importance of whole tissue-mechanics, rather than single cell-mechanics in controlling extrusion. Tissue compaction, stiffness, and cell-cell adhesion can impact the efficiency of cell extrusion and mechanisms that drive it, to adapt to different conditions during development or disease.

Identification of the soluble EphA7-interacting protein Nicalin as a regulator of EphA7 expression

A soluble form of EphA7 (sEphA7) has been found to antagonize the role of full-length EphA7 (EphA7-FL) to stabilize the membrane level of the tight junction protein Claudin6 (CLDN6) during Xenopus pronephros development. However, the mechanism underlying this antagonistic effect remains unclear. In this study, we identified Nicalin, a Nicastrin-like protein, as a novel sEphA7-interacting protein using immunoprecipitation (IP)/mass spectrometry (MS). In HEK293 cells, Nicalin interacted with sEphA7 and they predominantly co-localized in the endoplasmic reticulum (ER). Interestingly, Nicalin diminished the protein level of sEphA7 in the membranous fraction but increased that in the insoluble cytoplasmic fraction with a reduced molecular weight, suggesting that Nicalin restricts the entry of sEphA7 into the ER for further modification. sEphA7 probably acted as a chaperone and enhanced the membrane level of EphA7-FL and the formation of EphA7 complex, however, this effect was reversed by Nicalin. Our work suggested that Nicalin limits sEphA7 secretion, thereby preventing the formation of EphA7 complex. These results demonstrated the potential role of Nicalin in regulating EphA7 expression and revealed a potential mechanism underlying the antagonistic effect between sEphA7 and EphA7-FL.