| Feature | Evidence summary | Key references with year | DOI URL |
|---|---|---|---|
| Identity and core annotation | Verified target is **Schizosaccharomyces pombe Cdc15**, an essential cytokinesis scaffold and founding PCH/F-BAR family member; literature consistently describes the same protein architecture and function as the UniProt entry (F-BAR/FCH-region plus C-terminal SH3; essential for contractile ring/cytokinesis) (pqac-00000017, pqac-00000018, pqac-00000021, pqac-00000023) | Wachtler et al., 2006; Roberts-Galbraith et al., 2010; Bhattacharjee et al., 2023; Roberts-Galbraith et al., 2009 | https://doi.org/10.1091/mbc.e05-11-1086; https://doi.org/10.1016/j.molcel.2010.06.012; https://doi.org/10.7554/eLife.83062; https://doi.org/10.1083/jcb.200806044 |
| Domains | Cdc15 contains an **N-terminal F-BAR/FCH membrane-binding domain**, a **central intrinsically disordered region (IDR)**, and a **C-terminal SH3 domain**. The F-BAR mediates membrane binding/oligomerization and direct binding to Cdc12/Pxl1; the IDR is essential and heavily phosphoregulated; the SH3 recruits multiple ring proteins and is partly redundant with Imp2 SH3 (pqac-00000011, pqac-00000012, pqac-00000021, pqac-00000023) | Mangione et al., 2019; Snider et al., 2020; Bhattacharjee et al., 2023; Roberts-Galbraith et al., 2009 | https://doi.org/10.1091/mbc.e19-06-0314; https://doi.org/10.1016/j.celrep.2020.108526; https://doi.org/10.7554/eLife.83062; https://doi.org/10.1083/jcb.200806044 |
| Localization | Cell-cycle-dependent localization: **cortical patches at cell tips in interphase** and **medial cortex/contractile ring during mitosis/cytokinesis**. Dephosphorylation correlates with relocalization from mainly cytosolic/interphase pools to the division site (pqac-00000001, pqac-00000004, pqac-00000021) | Roberts-Galbraith et al., 2010; Wachtler et al., 2006; Bhattacharjee et al., 2023 | https://doi.org/10.1016/j.molcel.2010.06.012; https://doi.org/10.1091/mbc.e05-11-1086; https://doi.org/10.7554/eLife.83062 |
| Primary molecular function | Main role is as a **membrane–cytoskeleton scaffold for contractile ring assembly, anchoring, integrity, and constriction**. Cdc15 links the plasma membrane to actomyosin ring components and signaling proteins rather than acting as an enzyme or transporter (pqac-00000000, pqac-00000013, pqac-00000021) | Roberts-Galbraith et al., 2010; Snider et al., 2020; Bhattacharjee et al., 2023 | https://doi.org/10.1016/j.molcel.2010.06.012; https://doi.org/10.1016/j.celrep.2020.108526; https://doi.org/10.7554/eLife.83062 |
| Key partners and pathway links | Supported partners include **Cdc12**, **Myo1**, **Pxl1**, **Fic1**, **Cyk3**, **Rng2**, and functional overlap with **Imp2**. Cdc15 also promotes **calcineurin** recruitment through Pxl1-associated interfaces and participates in pathways linked to **SIN-dependent ring formation** and cytokinesis control (pqac-00000001, pqac-00000008, pqac-00000009, pqac-00000013) | Roberts-Galbraith et al., 2010; Roberts-Galbraith et al., 2009; Snider et al., 2020 | https://doi.org/10.1016/j.molcel.2010.06.012; https://doi.org/10.1083/jcb.200806044; https://doi.org/10.1016/j.celrep.2020.108526 |
| F-BAR-specific mechanism | The **concave F-BAR surface** binds membranes, while the **opposite surface** binds protein ligands such as **Cdc12** and **Pxl1**, creating a membrane platform that coordinates cytoskeletal and signaling components. F-BAR oligomerization is important for stable ring architecture (pqac-00000012, pqac-00000013, pqac-00000014) | Snider et al., 2020; Roberts-Galbraith et al., 2010 | https://doi.org/10.1016/j.celrep.2020.108526; https://doi.org/10.1016/j.molcel.2010.06.012 |
| SH3-specific mechanism | The **SH3 domains of Cdc15 and Imp2 cooperatively recruit Pxl1 and Fic1** to the contractile ring. These SH3-mediated interactions are important for ring integrity and preventing fragmentation, but the SH3 domain is not the sole essential function of Cdc15 (pqac-00000009, pqac-00000010, pqac-00000011, pqac-00000023) | Roberts-Galbraith et al., 2009; Mangione et al., 2019 | https://doi.org/10.1083/jcb.200806044; https://doi.org/10.1091/mbc.e19-06-0314 |
| IDR-specific mechanism | The **central IDR is uniquely essential** and cannot be replaced by the Imp2 IDR. Partial IDR deletions impair contractile ring integrity/circularity and abolish calcineurin localization, indicating a nonredundant regulatory/scaffold role beyond simple linker function (pqac-00000011, pqac-00000021) | Mangione et al., 2019; Bhattacharjee et al., 2023 | https://doi.org/10.1091/mbc.e19-06-0314; https://doi.org/10.7554/eLife.83062 |
| Phosphoregulation | Cdc15 is **hyperphosphorylated in interphase** and becomes **hypophosphorylated during mitosis/cytokinesis**. Dephosphorylation promotes an open conformation, oligomerization, membrane association, and partner binding; phosphorylation restrains cortical localization and assembly. **Clp1** contributes to dephosphorylation, and multiple kinases including **Pom1, Kin1, Shk1/Pak1, Pck1** phosphorylate the IDR (pqac-00000000, pqac-00000001, pqac-00000004, pqac-00000015, pqac-00000021) | Wachtler et al., 2006; Roberts-Galbraith et al., 2010; Bhattacharjee et al., 2023 | https://doi.org/10.1091/mbc.e05-11-1086; https://doi.org/10.1016/j.molcel.2010.06.012; https://doi.org/10.7554/eLife.83062 |
| Phase separation / condensates | Recent work shows that **dephosphorylated Cdc15 undergoes LLPS-like droplet formation in vitro** and forms **PM-bound condensates in cells**; phosphorylation by multiple polarity kinases inhibits this behavior and antagonizes cytokinetic ring assembly (pqac-00000003, pqac-00000007, pqac-00000015) | Bhattacharjee et al., 2023 | https://doi.org/10.7554/eLife.83062 |
| Phenotypes of perturbation | Loss or dysregulation of Cdc15 causes **elongated multinucleate/septation-defective cells**, unstable or fragmented rings, delayed ring formation, abnormal constriction, and cytokinetic failure. Combined loss of Cdc15/Imp2 SH3 functions abolishes ring formation; F-BAR or IDR defects destabilize rings and can be lethal (pqac-00000004, pqac-00000009, pqac-00000010, pqac-00000011, pqac-00000014) | Wachtler et al., 2006; Roberts-Galbraith et al., 2009; Mangione et al., 2019; Roberts-Galbraith et al., 2010 | https://doi.org/10.1091/mbc.e05-11-1086; https://doi.org/10.1083/jcb.200806044; https://doi.org/10.1091/mbc.e19-06-0314; https://doi.org/10.1016/j.molcel.2010.06.012 |
| Quantitative data | Reported quantitative findings include: **F-BAR = aa 19-295**; **≥35 phosphorylation sites** in interphase-regulated Cdc15; hypophosphorylated Cdc15 membrane association **49.1% vs 24.1%** for a more phosphorylated state; dephosphorylated oligomers with **~30.1 nm periodicity** and **~9.6 nm thickness**; **Cdc12 peptide binding Kd ≈ 5 µM** with **n = 0.5** per Cdc15 dimer; **cdc15-3A** causes **~40% reduced Cdc12 at the ring**, **~30% abnormal cells**, and a **~35% shallower ring**; LLPS assays used **10 µM** protein (pqac-00000001, pqac-00000007, pqac-00000012, pqac-00000013) | Roberts-Galbraith et al., 2010; Snider et al., 2020; Bhattacharjee et al., 2023 | https://doi.org/10.1016/j.molcel.2010.06.012; https://doi.org/10.1016/j.celrep.2020.108526; https://doi.org/10.7554/eLife.83062 |
| Current expert synthesis | Recent review literature places Cdc15 among the two major phosphoregulated actomyosin ring scaffold proteins in fission yeast and emphasizes its roles in **ring assembly, constriction, septation coordination, and possibly ESCRT-linked late cytokinesis context** (pqac-00000006) | Rezig et al., 2024 | https://doi.org/10.3390/jof10020154 |


*Table: This table summarizes experimentally supported functional annotation for Schizosaccharomyces pombe Cdc15 (UniProt Q09822), including domains, localization, interactions, regulation, phenotypes, and quantitative findings. It is restricted to evidence from the gathered primary studies and recent review requested.*