Biology subjects

Wu, J.-Q.

Publications and source records attributed to Wu, J.-Q..

4 recordsLinked to original sources

bioRxiv2025

Localizations and functions of septins are susceptible to epitope tagging

Septins are hetero-oligomeric cytoskeletal proteins that assemble into filaments and scaffolds on the plasma membrane to aid cytokinesis, morphogenesis, and other cellular processes. Epitope tagging is widely used to study septin localization and function. However, functionality testing of tagged septins is often insufficient because of technical challenges. Fission yeast provides an ideal genetic system to test functionalities and localizations of tagged septins. mEGFP/mYFP tagged septins Spn1 and Spn4 localize exclusively to the division site as double rings during cytokinesis, but tdTomato tagged septins also localize to puncta or short linear structures across the plasma membrane. It was proposed that these additional septin structures serve as diffusion barriers and are important for the localizations and functions of several proteins, including the NDR-kinase Sid2 and active Cdc42 GTPase. By analyzing cell morphology, cytokinesis defects, and genetic interactions between tagged septins and three mutations, we find that septins are less functional with tdTomato or 3HA than other tags. Additionally, Sid2 appearance at the division site is after septins and delayed in septin deletions, contrary to previous reports. Our data re-emphasize the need for rigorous functional tests of tagged septins and for caution in interpreting function and localization data when using epitope tagged septins. SIGNIFICANCE STATEMENTO_LIFission yeast septins Spn1 and Spn4, expressed under their native promoters, have drastically different localizations depending on the fluorescent tag used. C_LIO_LIBy assessing cell morphology, cytokinesis defects, cell integrity, and genetic interactions between tagged septins and other mutations, we find that septins are less functional when tagged with tdTomato/3HA compared to mEGFP/mYFP. C_LIO_LIOur data highlight the need for rigorous functional tests of tagged septins and caution when interpreting localization/function data because septin polymers are susceptible to perturbations by epitope tags. Our results also caution the caveats of using epitope tags to study other proteins, which is almost indispensable. C_LI

cell biology↗

bioRxiv2025

Spatial control of secretory vesicle targeting by the Ync13-Rga7-Rng10 complex during cytokinesis

Cytokinesis requires precise coordination of contractile-ring constriction, vesicle trafficking and fusion to the plasma membrane, and extracellular matrix assembly/remodeling at the cleavage furrow to ensure faithful cell division and maintain cell integrity. These processes and proteins involved are broadly conserved across eukaryotes, yet molecular mechanisms controlling the spatiotemporal pathways of membrane trafficking remain poorly understood. Here, using fission yeast genetics, microscopy, and in vitro binding assays, we identify a conserved module including the Munc13 protein Ync13, F-BAR protein Rga7, and coiled-coil protein Rng10 to be critical for precise and selective vesicle targeting during cytokinesis. The module specifically recruit the TRAPP-II but not exocyst complex to tether vesicles containing the glucan synthases Bgs4 and Ags1 along the cleavage furrow. Ync13 subsequently interacts with the SM protein Sec1 for vesicle fusion. Mutations in this pathway disrupt septum integrity and lead to cell lysis. Our work provides key insights into how membrane trafficking is tightly controlled to maintain cell integrity during cytokinesis.

cell biology↗

bioRxiv2025

Roles of the MO25 protein Pmo25 in contractile-ring stability and localization of the NDR kinase Sid2 during cytokinesis

Mouse protein-25 (MO25) family proteins are crucial in development and morphogenesis from plants to humans. The fission yeast MO25 protein Pmo25 is essential for cell polarity and division. However, how Pmo25 regulates cytokinesis remains largely unknown. Here we found that the actomyosin contractile ring and septum formation were defective during cytokinesis in pmo25 mutants. Pmo25 physically and genetically interacted with the myosin-II light chain Cdc4, which is essential for the contractile-ring assembly and function. Additionally, pmo25 mutations had synthetic genetic interactions with all other tested mutations in contractile-ring proteins. Moreover, Pmo25 colocalized with the NDR kinase Sid2 and participated in its recruitment to the division plane. Furthermore, Pmo25 directly bound the Munc13/UNC-13 protein Ync13 and modulated the secretion of glucanase Eng1 to the division site for daughter-cell separation. Our data provide insight into how Pmo25 regulates cytokinesis and suggest that the conserved MO25 proteins can link various steps of cytokinesis.

cell biology↗

bioRxiv2024

Septins function in exocytosis via physical interactions with the exocyst complex in fission yeast cytokinesis

Septins can function as scaffolds for protein recruitment, membrane-bound diffusion barriers, or membrane curvature sensors. Septins are important for cytokinesis, but their exact roles are still obscure. In fission yeast, four septins (Spn1 to Spn4) accumulate at the rim of the division plane as rings. The octameric exocyst complex, which tethers exocytic vesicles to the plasma membrane, exhibits a similar localization and is essential for plasma membrane deposition during cytokinesis. Without septins, the exocyst spreads across the division plane but absent from the rim during septum formation. These results suggest that septins and the exocyst physically interact for proper localization and function. Indeed, we predicted six pairs of interactions between septin and exocyst subunits by AlphaFold, most of them are confirmed by co-immunoprecipitation and yeast two-hybrid assays. Exocyst mislocalization results in mistargeting of secretory vesicles and their cargos, which leads to cell-separation delay in septin mutants. Our results indicate that septins guide the targeting of exocyst complex on the plasma membrane for vesicle tethering during cytokinesis through physical interactions.

cell biology↗