Biology subjects

Shinoda, N.

Publications and source records attributed to Shinoda, N..

4 recordsLinked to original sources

bioRxiv2025

Bruce suppresses autophagy-regulated caspase activity and wing tissue growth in Drosophila

Caspases are cysteine-aspartic proteases that mediate both lethal and non-lethal cellular outcomes, including the promotion of tissue growth. However, the mechanisms underlying the differential regulation of these activities remain unclear. We have previously shown that among the two Drosophila executioner caspases, Dcp-1 and Drice, Dcp-1 promotes tissue growth in a non-lethal manner, independent of canonical apoptotic signaling. Herein, we demonstrated that overexpressed Dcp-1, but not Drice, was activated without canonical apoptosome components. TurboID-based proximity labeling revealed distinct proximal proteomes, among which Sirtuin 1, an Atg8a deacetylase, which promotes autophagy, was specifically required for Dcp-1 activation. Autophagy-related genes, including Bcl-2 family members Debcl and Buffy, are required for Dcp-1 activation. Structure-based prediction using AlphaFold3 further identified Bruce, an autophagy-regulated inhibitor of apoptosis, as a Dcp-1-specific regulator acting outside the apoptosome-mediated pathway. Physiologically, Bruce suppresses wing tissue growth. These findings indicate that non-lethal Dcp-1 activity is governed by the autophagy-Bruce axis, enabling distinct non-lethal functions independent of cell death.

developmental biology↗

bioRxiv2025

Early-peaking caspase-7 activity at the plasma membrane drives apoptotic phosphatidylserine exposure

Apoptosis is an immunologically silent form of regulated cell death executed by caspase1. Caspase cleaves hundreds of substrates throughout the cell to regulate apoptotic processes2, including phosphatidylserine (PS) externalization3-5. However, spatio-temporal regulation of caspase activity in dying cells remains unclear. Here, we show that caspase activity peaks earlier at the plasma membrane (PM) during apoptosis by establishing a Dual Forster resonance energy transfer (Dual FRET) imaging system that combines subcellularly targeted FRET-based caspase biosensors with a cytosolic reference counterpart6,7. Genetic analysis identified caspase-7, an executioner caspase considered an inefficient backup for caspase-3, the major executioner caspase8,9, as a caspase responsible for the Early-Peaking Caspase Activity at the PM (EP-CAP). Mechanistically, EP-CAP is mediated via electrostatic interactions between PS in the inner leaflet of the PM and polybasic residues in the N-terminal intrinsically disordered region (IDR) of caspase-7, which are liberated by the caspase-mediated removal of polyacidic residues. Physiologically, EP-CAP facilitates the efficient cleavage of phospholipid scramblases for the rapid externalization of PS and subsequent efferocytosis. Accordingly, we propose that caspase-7, but not caspase-3, is a bona fide immunologically silent death caspase reinforcing the non-inflammatory nature of apoptosis via EP-CAP.

cell biology↗

bioRxiv2024

A Nonsecretory Antimicrobial Peptide Mediates Inflammatory Organ Damage in Drosophila Renal Tubules

An excessive immune response damages organs, yet its molecular mechanism is incompletely understood. In this study, we used Drosophila renal tubules as a model to screen a factor mediating organ damage upon genetic activation of an innate immune Imd signalling pathway. We identified an antimicrobial peptide, Attacin-D (AttD), which causes organ damage upon Imd activation in the Malpighian tubules. Loss of AttD function suppresses most of the pathological phenotypes induced by Imd activation, such as cell death, compensatory stem cell proliferation, bloating of whole animal, susceptibility to a high salt diet, elevation of purine levels, and mortality, without compromising the immune activation. AttD is required for the immune-induced damage specifically in the Malpighian tubules but not the midgut. Interestingly, AttD uniquely lacks the signal peptide and is not secreted out from cells. Suppression of AttD almost completely attenuates mortality induced by gut tumour-induced immune activation. Our study elucidates the mechanistic effector of immune-induced organ damage.

immunology↗

bioRxiv2023

Executioner caspase is proximal to Fasciclin 3 which facilitates non-lethal activation in Drosophila olfactory receptor neurons

The nervous system undergoes functional modification independent on cell turn over. Caspase participates in reversible neuronal modulation via non-lethal activation. However, the mechanism that enables non-lethal activation remains unclear. Here, we analyzed proximal proteins of Drosophila executioner caspase in the adult brain using TurboID. We discovered that executioner caspase Drice is, as an inactive proform, proximal to cell membrane proteins, including a specific splicing isoform of cell adhesion molecule Fasciclin 3 (Fas3), Fas3G. To investigate whether sequestration of executioner caspase to plasma membrane of axons is the mechanism for non-lethal activation, we developed a Gal4-Manipulated Area-Specific CaspaseTracker/CasExpress system for sensitive monitoring of caspase activity near plasma membrane. We demonstrated that Fas3G-overexpression promotes caspase activation in olfactory receptor neurons without killing them, by inducing expression of initiator caspase Dronc, which also comes close to Fas3G. Physiologically, Fas3G overexpression-facilitated non-lethal caspase activation suppresses innate olfactory attraction behavior. Our findings suggest that subcellularly-restricted caspase activation, defined by caspase proximal proteins, is the mechanism for non-lethal activation, opening the methodological development of reversible modification of neuronal function via regulating caspase proximal proteins.

molecular biology↗