Biochemical Large-Scale Interaction Analysis of Murine Olfactory Receptors and Associated Signaling Proteins with Post-Synaptic Density 95, Drosophila Discs Large, Zona-Occludens 1 (PDZ) Domains

Hippo Signaling in Cancer: Lessons From Drosophila Models

Hippo pathway was initially identified through genetic screens for genes regulating organ size in fruitflies. Recent studies have highlighted the role of Hippo signaling as a key regulator of homeostasis, and in tumorigenesis. Hippo pathway is comprised of genes that act as tumor suppressor genes like hippo (hpo) and warts (wts), and oncogenes like yorkie (yki). YAP and TAZ are two related mammalian homologs of Drosophila Yki that act as effectors of the Hippo pathway. Hippo signaling deficiency can cause YAP- or TAZ-dependent oncogene addiction for cancer cells. YAP and TAZ are often activated in human malignant cancers. These transcriptional regulators may initiate tumorigenic changes in solid tumors by inducing cancer stem cells and proliferation, culminating in metastasis and chemo-resistance. Given the complex mechanisms (e.g., of the cancer microenvironment, and the extrinsic and intrinsic cues) that overpower YAP/TAZ inhibition, the molecular roles of the Hippo pathway in tumor growth and progression remain poorly defined. Here we review recent findings from studies in whole animal model organism like Drosophila on the role of Hippo signaling regarding its connection to inflammation, tumor microenvironment, and other oncogenic signaling in cancer growth and progression.

NHERF1 in Microvilli of Vomeronasal Sensory Neurons

In most mammals, the vomeronasal system detects a variety of (semio)chemicals that mediate olfactory-driven social and sexual behaviors. Vomeronasal chemosensation depends on G protein-coupled receptors (V1R, V2R, and FPR-rs) that operate at remarkably low stimulus concentrations, thus, indicating a highly sensitive and efficient signaling pathway. We identified the PDZ domain-containing protein, Na⁺/H⁺ exchanger regulatory factor-1 (NHERF1), as putative molecular organizer of signal transduction in vomeronasal neurons. NHERF1 is a protein that contains 2 PDZ domains and a carboxy-terminal ezrin-binding domain. It localizes to microvilli of vomeronasal sensory neurons and interacts with V1Rs. Furthermore, NHERF1 and Gα_i2 are closely colocalized. These findings open up new aspects of the functional organization and regulation of vomeronasal signal transduction by PDZ scaffolding proteins.

Deconstructing the molecular architecture of olfactory areas using proteomics

The anatomy of the olfactory system is highly complex, comprising a system of olfactory receptors, pathways for the transmission of olfactory information, and structures for the recognition, discrimination, and memorization of odors. During the last years, proteomics has emerged as a large-scale comprehensive approach to characterize and quantify specific olfactory-related proteomes in different biological conditions such as olfactory learning, neurodegeneration, and ageing between others. The current work reviews recent applications of proteomics to olfaction with particular focus on quantitative proteome profiling studies performed on olfactory areas from laboratory animal models as well as proteomic characterizations performed on specific brain structures and fluids involved in human smell. Finally, we will also discuss the potential application of proteomics to study global proteome dynamics and posttranslationally modified proteomes in order to unravel cell-signaling networks that occur from peripheral structures to olfactory cortical areas during odor processing.

Impact of the Usher syndrome on olfaction

Usher syndrome is a genetically and clinically heterogeneous disease in humans, characterized by sensorineural hearing loss, retinitis pigmentosa and vestibular dysfunction. This disease is caused by mutations in genes encoding proteins that form complex networks in different cellular compartments. Currently, it remains unclear whether the Usher proteins also form networks within the olfactory epithelium (OE). Here, we describe Usher gene expression at the mRNA and protein level in the OE of mice and showed interactions between these proteins and olfactory signaling proteins. Additionally, we analyzed the odor sensitivity of different Usher syndrome mouse models using electro-olfactogram recordings and monitored significant changes in the odor detection capabilities in mice expressing mutant Usher proteins. Furthermore, we observed changes in the expression of signaling proteins that might compensate for the Usher protein deficiency. In summary, this study provides novel insights into the presence and purpose of the Usher proteins in olfactory signal transduction.