Swain, R. K. | bioRxiv Science

bioRxiv2020

miR-142 regulates IL-6 signalling during host immune response to Staphylococcus epidermidis infection in zebrafish

Host immune responses to Staphylococcus epidermidis, a frequent cause of nosocomial infections, are not well understood. We have established a novel bath immersion model of this infection in zebrafish larvae. S.epidermidis infection activates Tlr-2 signalling pathway by upregulation of tlr-2. Macrophages play a primary role in the host immune response and are involved in clearance of infection in the larvae. There is marked inflammation characterised by heightened NF-{kappa}B signalling and elevation of several pro-inflammatory cytokines. Infected larvae show rapid upregulation of il-1b and tnf-a transcripts and relatively slower elevation of il-6 transcription. The IL-6 signalling pathway is additionally subject to amplification by elevation of IL-6 signal transducer (il-6st) levels, which negatively correlates with miRNA dre-miR-142-5p expression. Enhanced IL-6 signalling is protective to the host in this model as inhibition of the signalling pathway resulted in increased mortality upon S.epidermidis infection. Our study describes the host immune responses to S.epidermidis infection, identifies a likely role for miR-142-5p - il-6st interaction in modulating this response and establishes the importance of IL-6 signalling in this infection model.

immunology↗

bioRxiv2019

Allosteric feed-forward activation of AP-2 via FCHO- BMP2K axis promotes clathrin-mediated endocytosis

Spatio-temporal regulation of central adaptor complex, AP-2 is pivotal for clathrin-mediated endocytosis (CME). We recently discovered that FCHO proteins trigger clathrin-coated pit (CCP) formation by allosterically activating AP-2 on plasma membrane (Umasankar et al., 2014). Here, we demonstrate that this activation promotes AP-2 phosphorylation via recruitment and stabilization of BMP-2 inducible kinase (BMP2K), a bona fide AP-2 kinase leading to CCP maturation. Accordingly, BMP2K mislocalizes and degrades in FCHO knockout/ AP-2 depleted cells. Functional inactivation of kinase impairs AP-2 phosphorylation leading to altered lattice morphology and CME phenotypes reminiscent of CCP maturation defects. Reexpression of FCHO rescues AP-2 phosphorylation defects in FCHO knockout cells implying membrane activation of AP-2 is a prerequisite for kinase function. Furthermore, gain- and loss-of function phenotypes of FCHO and BMP2K are analogous and mirror altered AP-2 functions during zebrafish embryogenesis. Together, our findings reveal an in vivo allosteric feed-forward axis for operation of CME.

cell biology↗