Biology subjects

Roussa, E.

Publications and source records attributed to Roussa, E..

3 recordsLinked to original sources

bioRxiv2023

TGF-beta2 regulates neuronal Ankyrin-G and promotes its interaction with KCC2

The neuronal K+/Cl- cotransporter 2 (KCC2) is the major Cl- extruder in CNS neurons and responsible for fast hyperpolarizing postsynaptic inhibition in mature neurons. Impaired KCC2 function has been associated with several brain pathologies. KCC2 forms immunocomplexes with several proteins that may regulate KCC2 membrane trafficking, stability and function, thus, tuning important cellular processes, including chloride homeostasis and dendritic spine development. In the brain, the scaffold protein Ankyrin-G, encoded by the Ank3 gene, is expressed in several isoforms with distinct spatial and temporal expression patterns, is regulated by TGF-{beta} signalling and is proposed as a KCC2 interaction partner. Moreover, Ank3 gene has been implicated in several neuropsychiatric disorders. Here, we investigated a putative impact of transforming growth factor beta 2 (TGF-{beta}2) on KCC2/Ankyrin-G interaction using quantitative RT-PCR, immunoblotting, immunoprecipitation and immunofluorescence in mouse immature and differentiated hippocampal neurons and in forebrain and brainstem tissue from Tgf-{beta}2 deficient mice. The results show TGF-{beta}2-dependent downregulation of Ank3 transcripts, as well as KCC2/Ankyrin-G interaction in mouse brainstem tissue at embryonic day (E) 17.5. In vitro, loss of Tgf-{beta}2 resulted in significantly reduced axonal and somatic Ankyrin-G in immature neurons and significantly reduced somatic Ankyrin-G abundance in differentiated mouse hippocampal neurons. Membrane abundance of Ankyrin-G was downregulated in Tgf-{beta}2 mutants as well, a phenotype rescued by application of exogenous TGF-{beta}2. Moreover, the results suggest the presence of a Golgi-associated Ankyrin-G isoform in neurons and significantly impaired membrane KCC2 abundance following knock down of Ank3. Thus, the present study provides new insights into Ankyrin-G regulation by TGF-{beta}2 in neurons and first evidence of a TGF-{beta}2-regulated interaction of KCC2 with Ankyrin-G. Moreover, these results strengthen the notion for TGF-{beta}2 as pivotal regulator of KCC2 abundance and function.

neuroscience↗

bioRxiv2022

LRBA balances antigen presentation and T-cell responses by facilitating autophagy through the binding to PIK3R4 and FYCO1

Reduced autophagy is associated with the aberrant humoral response observed in lipopolysaccharide-responsive beige-like anchor protein (LRBA) deficiency; however, the exact molecular mechanism and its impact on T-cell responses remain unknown. We identified two novel LRBA interactors, phosphoinositide 3-kinase regulatory subunit 4 (PIK3R4) and FYVE And Coiled-Coil Domain Autophagy Adaptor 1 (FYCO1). Both proteins play essential roles in different stages of autophagy. PIK3R4 facilitates the production of phosphatidylinositol-3 phosphate (PI(3)P) required for autophagosome formation and autophagosome-lysosome fusion, whereas FYCO1 allows autophagosome movement. LRBA-KO cells showed an impaired PI(3)P production, a delayed autophagosome-lysosome fusion, an accumulation of enlarged autophagosomes, and an atypical lysosomal positioning. These abnormalities led to decreased cargo material degradation and prolonged antigen presentation to T-cells via autophagy, resulting in increased production of proinflammatory cytokines, as autophagy is a major intracellular degradation system for major histocompatibility class II complex (MHCII) loading. Aberrant autophagosome formation, cargo degradation and antigen presentation were rescued by ectopic expression of WT-LRBA. In summary, we identified a novel function of LRBA that is crucial for T-cell-driven response through the interaction with two proteins of the autophagy machinery. These observations may contribute to the exacerbated T-cell dysregulation observed in LRBA-deficient patients.

immunology↗

bioRxiv2017

TGF(beta) Mediated Structural Remodeling Facilitates Optic Fissure Fusion And The Necessity Of BMP Antagonism In This Process

The optic fissure is a transient gap in the developing vertebrate eye, which must be closed as development proceeds. A persisting optic fissure, coloboma, is a major cause for blindness in children. Multiple factors are genetically linked to coloboma formation. However, especially the process of optic fissure fusion is still largely elusive on a cellular and molecular basis.\n\nWe found a coloboma phenotype in mice with a targeted inactivation of the transforming growth factor 2 (TGF{beta}2). Here the optic fissure margins got in touch, however, failed to fuse. Transcriptomic analyses indicated TGF{beta} mediated ECM remodeling during optic fissure fusion. For functional analyses, we switched model systems and made use of zebrafish. We found TGF{beta} ligands expressed in the developing zebrafish eye, and the ligand binding receptor in the optic fissure. Using a new in vivo TGF{beta} signaling reporter, we also found active TGF{beta} signaling in the margins of the optic fissure. We addressed the function of Cadherin 6 (cdh6), one of the TGF{beta} regulated genes, by knock down experiments in zebrafish and found a prominent coloboma phenotype. Cdh6 was often found involved in processes of epithelial to mesenchymal transition (EMT), strengthening our hypothesis that an EMT-like process is also necessary for optic fissure fusion. Furthermore, we found Gremlin 2b (grem2b) and Follistatin a (fsta), homologs of TGF{beta} regulated bone morphogenetic protein (BMP) antagonists, expressed in the optic fissure margins, indicating the necessity of a localized inhibition of BMP signaling. Finally, we show that induced BMP expression is sufficient to inhibit optic fissure fusion. Together with our previous findings this indicates a dual role of BMP signaling during optic fissure closure.\n\nSummary statementTGF{beta} is crucial for optic fissure fusion, involving cdh6. TGF{beta} mediated optic fissure fusion is potentially hampered by BMP signaling, which is blocked by TGF{beta} induced BMP antagonists within the optic fissure margins.

developmental biology↗