FEBS Letters

doi: 10.1002/1873-3468.14383pmid: N/A

Nishio, Joichiro; Takahashi, Yoshiaki; Kasahara, Masahiro; Takeda, Yoichi; Kikuma, Takashi

doi: 10.1002/1873-3468.14589pmid: 36700830

Autophagy is classified into nonselective and selective autophagy, depending on the specificity of substrate degradation. In the filamentous fungus Aspergillus oryzae, selective autophagy, which includes pexophagy and mitophagy, has been observed. However, the molecular mechanism underlying selective autophagy in filamentous fungi remains unclear. Here, we identified a novel protein that interacts with the autophagy‐related protein Atg8 in A. oryzae, named AoAtg8‐interacting protein A (AeiA). AeiA was localized to AoAtg8‐positive autophagic membrane structures and peroxisomes. Moreover, peroxisomal trafficking into the vacuole was reduced in AeiA disruptants. Taken together, AeiA is a novel selective autophagy‐related protein that contributes to pexophagy in A. oryzae.

Feng, Hui; Liu, Xiao; Zhou, Chenqian; Gu, Qiuchen; Li, Ye; Chen, Jianguo; Teng, Junlin; Zheng, Pengli

doi: 10.1002/1873-3468.14575pmid: 36650560

Autophagy and Hippo signalling pathways both play important roles in cell homeostasis and are often involved in tumourigenesis. However, the crosstalk between these two signal pathways in response to stress conditions, such as nutrient deficiency, is incompletely understood. Here, we show that vesicular localised coiled‐coil domain containing 115 (CCDC115) inhibits autophagy as well as Hippo signalling pathway under starvation. Moreover, we show that CCDC115 interacts with the HOPS complex. This interaction competes with STX17, thus inhibiting the fusion of autophagosomes with lysosomes. Hence, CCDC115 inhibits the autophagic degradation of yes‐associated protein (YAP), thereby promoting cell proliferation in nutrient‐restricted situation.

Suzuki, Kuninori; Hirata, Eri

doi: 10.1002/1873-3468.14509pmid: 36217212

Aminopeptidase I (Ape1) is one of the major cargoes of the cytoplasm‐to‐vacuole targeting (Cvt) pathway, which is a kind of selective autophagy, in Saccharomyces cerevisiae. After synthesis, the Ape1 precursor (prApe1) undergoes phase separation to form liquid droplets, termed Ape1 droplets, in the cytoplasm. In this study, we found that cells expressing prApe1‐GFP exhibited temperature‐sensitive formation of Ape1 droplets, which affected its transport. Moreover, we showed that endogenous Ape1 transport was defective at high temperatures in various laboratory strains due to the defect in the formation of Ape1 droplets at these temperatures. Finally, we found that gene disruptants showing heat‐tolerant growth suppressed the temperature sensitivity of the Ape1 transport. The formation of Ape1 droplets might be an indicator of cytoplasmic integrity at high temperature.

Onishi, Katsuya; Ishihara, Seiichiro; Takahashi, Masayuki; Sakai, Akihiro; Enomoto, Atsushi; Suzuki, Kentaro; Haga, Hisashi

doi: 10.1002/1873-3468.14592pmid: 36723402

Stiffness of the extracellular matrix regulates various biological responses, but the response mechanisms are poorly understood. Here, we found that the nuclear diphosphorylated myosin regulatory light chain (2P‐MRLC) is a critical mechanomediator that suppresses apoptosis in response to substrate stiffness. Stiff substrates promoted the nuclear localization of 2P‐MRLC. Zipper‐interacting protein kinase [ZIPK; also known as death‐associated protein kinase 3 (DAPK3)], a kinase for MRLC, was localized in the nucleus in response to stiff substrates and promoted the nuclear localization of 2P‐MRLC. Moreover, actin fiber formation induced by substrate stiffness promoted the nuclear localization of 2P‐MRLC via ZIPK. 2P‐MRLC in response to substrate stiffness suppressed the expression of MAF bZIP transcription factor B (MafB) and repressed apoptosis. These findings reveal a newly identified role of MRLC in mechanotransduction.

Harada, Kazuki; Takashima, Maoko; Kitaguchi, Tetsuya; Tsuboi, Takashi

doi: 10.1002/1873-3468.14580pmid: 36694275

Although exocytosis can be categorized into several forms based on docking dynamics, temporal regulatory mechanisms of the exocytotic forms are unclear. We explored the dynamics of glucagon‐like peptide‐1 (GLP‐1) exocytosis in murine GLUTag cells (GLP‐1‐secreting enteroendocrine L‐cells) upon stimulation with deoxycholic acid (DCA) or high K+ to elucidate the mechanisms regulating the balance between the different types of exocytotic forms (pre‐docked with the plasma membrane before stimulation; docked after stimulation and subsequently fused; or rapidly recruited and fused after stimulation, without stable docking). GLP‐1 exocytosis showed a biphasic pattern, and we found that most exocytosis was from the pre‐docked granules with the plasma membrane before stimulation, or granules rapidly fused to the plasma membrane without docking after stimulation. In contrast, granules docked with the plasma membrane after stimuli and eventually fused were predominant thereafter. Inhibition of actin polymerization suppressed exocytosis of the pre‐docked granules. These results suggest that the docking dynamics of GLP‐1 granules shows a time‐dependent biphasic shift, which is determined by interaction with F‐actin.

Rosenbloom, Aaron D.; Pollard, Thomas D.

doi: 10.1002/1873-3468.14571pmid: 36650956

Members of the Wiskott–Aldrich Syndrome protein (WASp) family activate Arp2/3 complex (actin‐related proteins 2 and 3 complex) to form actin filament branches. The proline‐rich domain (PRD) of WASp contributes to branching nucleation, and the PRD of budding yeast Las17 binds actin filaments [Urbanek AN et al. (2013) Curr Biol 23, 196–203]. Biochemical assays showed the recombinant PRD of fission yeast Schizosaccharomyces pombe Wsp1p binds actin filaments with micromolar affinity. Recombinant PRDs of both Wsp1p and Las17p slowed the elongation of actin filaments by Mg‐ATP‐actin monomers by half and slowed the spontaneous polymerization of Mg‐ATP‐actin monomers modestly. The affinity of PRDs of WASp‐family proteins for actin filaments is high enough to contribute to the reported stimulation of actin filament branching by Arp2/3 complex.

Tsuda, Natsumi; Fukagawa, Ryohei; Sueda, Shinji

doi: 10.1002/1873-3468.14568pmid: 36528783

During mitosis in metazoan species, the nuclear envelope (NE) undergoes breakdown, and its fragments are absorbed within the membranous network of the endoplasmic reticulum (ER). Past observations by fluorescence microscopy led researchers to think that the NE loses its identity when it is absorbed within the ER membrane. However, in our previous work, we developed a more specific labelling method and found evidence that the NE does not completely lose its identity during mitosis. In the present work, we conduct further experiments, the results of which support the idea that the NE partially retains its identity during mitosis.

Han, Kai; Huang, Shuhan; Kong, Jie; Yang, Yang; Shi, Lei; Ci, Yali

doi: 10.1002/1873-3468.14581pmid: 36694281

Endoplasmic reticulum (ER) is a highly complicated and dynamic organelle that actively changes its shape and communicates with other organelles. Visualization of ER in live cells is of great importance to understand cellular activities. Here, we designed a novel ER marker, RR‐mNeonGreen, which comprised an N‐terminal ER retention signal, a bright fluorescent protein (mNeonGreen), and a C‐terminal transmembrane region. Colocalization of RR‐mNeonGreen with mCherry‐KDEL verified that RR‐mNeonGreen perfectly labeled the ER. RR‐mNeonGreen showed better continuity of ER tubules when imaged by super‐resolution microscopy. Moreover, RR‐mNeonGreen is competent for live‐cell imaging of ER dynamics and tracing of the interaction between ER and mitochondria at high spatiotemporal resolution. In summary, RR‐mNeonGreen is a novel ER marker for super‐resolution live‐cell imaging with multiple merits.