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Background: Quantitative myocardial PET perfusion imaging requires partial volume corrections.Methods: Patients underwent ECG-gated, rest-dipyridamole, myocardial perfusion PET using Rb-82 decay corrected in Bq/cc for diastolic, systolic, and combined whole cycle ungated images. Diastolic partial volume correction relative to systole was determined from the systolic/diastolic activity ratio, systolic partial volume correction from phantom dimensions comparable to systolic LV wall thicknesses and whole heart cycle partial volume correction for ungated images from fractional systolic-diastolic duration for systolic and diastolic partial volume corrections.Results: For 264 PET perfusion images from 159 patients (105 rest-stress image pairs, 54 individual rest or stress images), average resting diastolic partial volume correction relative to systole was 1.14 ± 0.04, independent of heart rate and within ±1.8% of stress images (1.16 ± 0.04). Diastolic partial volume corrections combined with those for phantom dimensions comparable to systolic LV wall thickness gave an average whole heart cycle partial volume correction for ungated images of 1.23 for Rb-82 compared to 1.14 if positron range were negligible as for F-18.Conclusion: Quantitative myocardial PET perfusion imaging requires partial volume correction, herein demonstrated clinically from systolic/diastolic absolute activity ratios combined with phantom data accounting for Rb-82 positron range. [ABSTRACT FROM AUTHOR]

Objectives: The purpose of this study was to determine if combined intense lifestyle and pharmacologic lipid treatment reduce myocardial perfusion abnormalities and coronary events in comparison to usual-care cholesterol-lowering drugs and whether perfusion changes predict outcomes.Background: Lifestyle and lipid drugs separately benefit patients with coronary artery disease (CAD).Methods: A total of 409 patients with CAD, who underwent myocardial perfusion imaging by dipyridamole positron emission tomography at baseline and after 2.6 years, had quantitative size/severity of perfusion defects measured objectively by automated software with follow-up for five additional years for coronary artery bypass graft, percutaneous coronary intervention, myocardial infarction, or cardiac death. Patients were categorized blindly according to prospective, predefined criteria as "poor" treatment without diet or lipid drugs, or smoking; "moderate" treatment on American Heart Association diet and lipid-lowering drugs or on strict low-fat diet (<10% of calories) without lipid drugs; and "maximal" treatment with diet <10% of calories as fat, regular exercise, and lipid active drugs dosed to target goals of low-density lipoproteins <2.3 mmol/l (90 mg/dl), high-density lipoproteins >1.2 mmol/l (45 mg/dl), and triglycerides <1.1 mmol/l (100 mg/dl).Results: Over five years, coronary events occurred in 6.6%, 20.3%, and 30.6% of patients on maximal, moderate, and poor treatment, respectively (p = 0.001). Size/severity of perfusion abnormalities significantly decreased for patients receiving maximal treatment and increased for patients undergoing moderate and poor treatment (p = 0.003 and 0.0001, respectively). Combined intense lifestyle change plus lipid active drugs and severity/change of perfusion abnormalities independently predicted cardiac events.Conclusions: Intense lifestyle and pharmacologic lipid treatment reduce size/severity of myocardial perfusion abnormalities and cardiac events compared with usual-care cholesterol-lowering drugs. Perfusion changes parallel treatment intensity and predict outcomes. [ABSTRACT FROM AUTHOR]

Centrosomes and spindle pole bodies (SPB) are important for mitotic spindle formation and also serve as signaling platforms. In the fission yeast Schizosaccharomyces pombe, genetic ablation and high-resolution imaging indicate that the ɑ-helical Ppc89 is central to SPB structure and function. Here, we developed and characterized conditional and truncation mutants of ppc89. Alleles with mutations in two predicted ɑ-helices near the C-terminus were specifically defective in anchoring Sid4, the scaffold for the septation initiation network (SIN), and proteins dependent on Sid4 (Cdc11, Dma1, Mto1 and Mto2). Artificial tethering of Sid4 to the SPB fully rescued these ppc89 mutants. Another ppc89 allele had mutations located throughout the coding region. While this mutant was also defective in Sid4 anchoring, it displayed additional defects including fragmented SPBs and forming and constricting a second cytokinetic ring in one daughter cell. These defects were shared with a ppc89 allele truncated of the most C-terminal predicted ɑ-helices that is still able to recruit Sid4 and the SIN. We conclude that Ppc89 not only tethers the SIN to the SPB but is also necessary for the integrity of the SPB and faithful coordination of cytokinesis with mitosis., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Genetics Society of America.)

The CK1 family are conserved serine/threonine kinases with numerous substrates and cellular functions. The fission yeast CK1 orthologues Hhp1 and Hhp2 were first characterized as regulators of DNA repair, but the mechanism(s) by which CK1 activity promotes DNA repair had not been investigated. Here, we found that deleting Hhp1 and Hhp2 or inhibiting CK1 catalytic activities in yeast or in human cells increased double-strand breaks (DSBs). The primary pathways to repair DSBs, homologous recombination and nonhomologous end joining, were both less efficient in cells lacking Hhp1 and Hhp2 activity. To understand how Hhp1 and Hhp2 promote DNA damage repair, we identified new substrates of these enzymes using quantitative phosphoproteomics. We confirmed that Arp8, a component of the INO80 chromatin remodeling complex, is a bona fide substrate of Hhp1 and Hhp2 important for DNA repair. Our data suggest that Hhp1 and Hhp2 facilitate DNA repair by phosphorylating multiple substrates, including Arp8.

Cytokinesis is the final stage of the cell cycle that results in the physical separation of daughter cells. To accomplish cytokinesis, many organisms build an actin- and myosin-based cytokinetic ring (CR) that is anchored to the plasma membrane (PM). Defects in CR-PM anchoring can arise when the PM lipid phosphatidylinositol (4,5)-bisphosphate [PI(4,5)P2] is depleted. In Schizosaccharomyces pombe, reduced PM PI(4,5)P2 results in a CR that cannot maintain a medial position and slides toward one cell end, resulting in two differently sized daughter cells. S. pombe PM PI(4,5)P2 is synthesized by the phosphatidylinositol 4-phosphate 5-kinase (PI5-kinase) Its3, but what regulates this enzyme to maintain appropriate PM PI(4,5)P2 levels in S. pombe is not known. To identify Its3 regulators, we used proximity-based biotinylation, and the uncharacterized protein Duc1 was specifically detected. We discovered that Duc1 decorates the PM except at the cell division site and that its unique localization pattern is dictated by binding to the endoplasmic reticulum (ER)-PM contact site proteins Scs2 and Scs22. Our evidence suggests that Duc1 also binds PI(4,5)P2 and helps enrich Its3 at the lateral PM, thereby promoting PM PI(4,5)P2 synthesis and robust CR-PM anchoring., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Background: Data on cardiac positron emission tomography (PET) in liver transplantation (LT) candidates are limited with no prior study accounting for poorly metabolized caffeine reducing stress perfusion., Method: Consecutive LT candidates (n = 114) undergoing cardiac rest/stress PET were instructed to abstain from caffeine for 2 days extended to 5 and 7 days. Due to persistently high prevalence of measurable blood caffeine after 5-day caffeine abstinence, dipyridamole (n = 41) initially used was changed to dobutamine (n = 73). Associations of absolute flow, coronary flow reserve (CFR), detectable blood caffeine, and Modified End-Stage Liver Disease (MELD) score for liver failure severity were evaluated. Coronary flow data of LT candidates were compared to non-LT control group (n = 102 for dipyridamole, n = 29 for dobutamine)., Results: Prevalence of patients with detectable blood caffeine was 63.3%, 36.7% and 33.3% after 2-, 5- and 7-day of caffeine abstinence, respectively. MELD score was associated with detectable caffeine (odd ratio 1.18,P < 0.001). CFR was higher during dipyridamole stress without-caffeine versus with-caffeine (2.22 ± 0.80 vs 1.55 ± 0.37,P = 0.048) but lower than dobutamine stress (2.22 ± 0.80 vs 2.82 ± 1.02,P = 0.026). Mediation analysis suggested that the dominant association between CFR and MELD score in dipyridamole group derived from caffeine-impaired CFR and liver failure/caffeine interaction. CFR in LT candidates was lower than non-LT control population in both dipyridamole and dobutamine group., Conclusion: We demonstrate exceptionally high prevalence of detectable blood caffeine in LT candidates undergoing stress PET myocardial perfusion imaging resulting in reduced CFR with dipyridamole compared to dobutamine. The delayed caffeine clearance in LT candidates makes dobutamine a preferred stress agent in this population., (Copyright © 2024 University of Texas Health Science Center at Houston. Published by Elsevier Inc. All rights reserved.)

Centrosomes and spindle pole bodies (SPBs) are important for mitotic spindle formation and serve as cellular signaling platforms. Although centrosomes and SPBs differ in morphology, many mechanistic insights into centrosome function have been gleaned from SPB studies. In the fission yeast Schizosaccharomyces pombe , the α-helical protein Ppc89, identified based on its interaction with the septation initiation network scaffold Sid4, comprises the SPB core. High-resolution imaging has suggested that SPB proteins assemble on the Ppc89 core during SPB duplication, but such interactions are undefined. Here, we define a connection between Ppc89 and the essential pericentrin Pcp1. Specifically, we found that a predicted third helix within Ppc89 binds the Pcp1 pericentrin-AKAP450 centrosomal targeting (PACT) domain complexed with calmodulin. Ppc89 helix 3 contains similarity to p resent i n the N -terminus of C ep57 (PINC) motifs found in the centrosomal proteins fly SAS-6 and human Cep57 and also to the S. cerevisiae SPB protein Spc42. These motifs bind pericentrin-calmodulin complexes and AlphaFold2 models suggest a homologous complex assembles in all four organisms. Mutational analysis of the S. pombe complex supports the importance of Ppc89-Pcp1 binding interface in vivo. Our studies provide insight into the core architecture of the S. pombe SPB and suggest an evolutionarily conserved mechanism of scaffolding pericentrin-calmodulin complexes for mitotic spindle formation., Competing Interests: Conflicts of interests: The authors declare no financial conflict of interest.

Many organisms utilize an actin- and myosin-based cytokinetic ring (CR) to help complete cytokinesis. In Schizosaccharomyces pombe , the Septation Initiation Network (SIN) promotes proper CR function and stability. The SIN is a conserved and essential signaling network consisting of a GTPase and a cascade of kinases assembled at the spindle pole body (SPB). The PP2A SIN inhibitory phosphatase (SIP) complex related to the STRIPAK phosphatase complex is one inhibitor of SIN signaling. The SIP consists of Csc1, Csc2, Csc3, Csc4, Paa1, and the phosphatase subunit Ppa3. Here, we determine that the SIP is anchored at the SPB via the Csc1 FHA domain and that constitutive SPB localization of the SIP is lethal due to persistent SIN inhibition. Disrupting SIP docking at the SPB with a point mutation within the FHA domain or eliminating phosphatase activity by introducing a point mutation within Ppa3 resulted in intact SIP complexes without SIN inhibitory function. Lastly, we defined the unique features of Ppa3 that allow it, but not two other PP2A catalytic subunits, to incorporate into the SIP. Overall, we provide insight into how the SIP complex assembles, localizes, and functions to counteract the SIN with spatiotemporal precision during cytokinesis.

The Schizosaccharomyces pombe septation initiation network (SIN) promotes cytokinesis and septation. Comprised of a protein kinase cascade triggered by activation of a small GTPase and inhibited by a two-component GAP that localize to the spindle pole bodies in a cell cycle specific manner. Here, we characterized temperature-sensitive mutants isolated in the 1990s in four SIN components. We determined the mutations within each cdc14 , cdc16 , sid1 , and sid2 mutant allele and analyzed their growth at different temperatures compared with known mutant alleles. The new mutants described here expand the toolkit for studying SIN signaling., Competing Interests: The authors declare that there are no conflicts of interest present., (Copyright: © 2024 by the authors.)

The Schizosaccharomyces pombe GTPase, Spg1 , activates the septation initiation network (SIN) protein kinase cascade to trigger septation. In the absence of functional Spg1 , cells fail cytokinesis and become multinucleate. In this study, we characterize a set of temperature-sensitive spg1 alleles isolated in the 1990s. We identify the mutations within each new and previously characterized allele, characterize the extent of relative growth defects, and assess their interaction with other SIN alleles., Competing Interests: The authors declare that there are no conflicts of interest present., (Copyright: © 2024 by the authors.)

CK1 kinases participate in many signaling pathways, and their regulation is of meaningful biological consequence. CK1s autophosphorylate their C-terminal noncatalytic tails, and eliminating these tails increases substrate phosphorylation in vitro, suggesting that the autophosphorylated C-termini act as inhibitory pseudosubstrates. To test this prediction, we comprehensively identified the autophosphorylation sites on Schizosaccharomyces pombe Hhp1 and human CK1ε. Phosphoablating mutations increased Hhp1 and CK1ε activity toward substrates. Peptides corresponding to the C-termini interacted with the kinase domains only when phosphorylated, and substrates competitively inhibited binding of the autophosphorylated tails to the substrate binding grooves. Tail autophosphorylation influenced the catalytic efficiency with which CK1s targeted different substrates, and truncating the tail of CK1δ broadened its linear peptide substrate motif, indicating that tails contribute to substrate specificity as well. Considering autophosphorylation of both T220 in the catalytic domain and C-terminal sites, we propose a displacement specificity model to describe how autophosphorylation modulates substrate specificity for the CK1 family.

Glycosyl-phosphatidylinositol (GPI) anchored proteins are implicated in remodeling of the yeast cell wall during growth and division. Schizosaccharomyces pombe proteins, Psu1 , Dfg501 , and Dfg502 are predicted GPI anchored proteins with likely cell wall modifying activity. Here, we isolated and characterized null and temperature-sensitive alleles that will allow further analysis of the function of these proteins and S. pombe cell wall formation. Our data confirm that Psu1 is necessary for cell separation, maintaining proper cell shape, and viability. Additionally, we found that Dfg501 and Dfg502 share a redundant and essential function necessary for cell separation and viability., Competing Interests: The authors declare that there are no conflicts of interest present., (Copyright: © 2024 by the authors.)

Background: Mitogen-activated protein kinases (MAPKs) preserve cell homeostasis by transducing physicochemical fluctuations of the environment into multiple adaptive responses. These responses involve transcriptional rewiring and the regulation of cell cycle transitions, among others. However, how stress conditions impinge mitotic progression is largely unknown. The mitotic checkpoint is a surveillance mechanism that inhibits mitotic exit in situations of defective chromosome capture, thus preventing the generation of aneuploidies. In this study, we investigate the role of MAPK Pmk1 in the regulation of mitotic exit upon stress., Results: We show that Schizosaccharomyces pombe cells lacking Pmk1, the MAP kinase effector of the cell integrity pathway (CIP), are hypersensitive to microtubule damage and defective in maintaining a metaphase arrest. Epistasis analysis suggests that Pmk1 is involved in maintaining spindle assembly checkpoint (SAC) signaling, and its deletion is additive to the lack of core SAC components such as Mad2 and Mad3. Strikingly, pmk1Δ cells show up to twofold increased levels of the anaphase-promoting complex (APC/C) activator Cdc20 Slp1 during unperturbed growth. We demonstrate that Pmk1 physically interacts with Cdc20 Slp1 N-terminus through a canonical MAPK docking site. Most important, the Cdc20 Slp1 pool is rapidly degraded in stressed cells undergoing mitosis through a mechanism that requires MAPK activity, Mad3, and the proteasome, thus resulting in a delayed mitotic exit., Conclusions: Our data reveal a novel function of MAPK in preventing mitotic exit and activation of cytokinesis in response to stress. The regulation of Cdc20 Slp1 turnover by MAPK Pmk1 provides a key mechanism by which the timing of mitotic exit can be adjusted relative to environmental conditions., (© 2024. The Author(s).)

The Schizosaccharomyces pombe Gas family of β-1,3-glucanosyltransferases modify the cell wall by elongating β-1,3-glucan chains. While gas1Δ cells are inviable under standard laboratory growth conditions, they are viable in the presence of an osmotic stabilizer. Even under these conditions however, gas1Δ cells are slow-growing and display cell separation and morphology defects. Here, we isolated and characterized two gas1 temperature-sensitive alleles. Our data support that Gas1 is the primary S. pombe β-1,3-glucanosyltransferase important for cell separation and cell viability and provide useful tools for further analysis of S. pombe cell wall formation., Competing Interests: The authors declare that there are no conflicts of interest present., (Copyright: © 2024 by the authors.)

Schizosaccharomyces pombe Clp1 is a Cdc14-family phosphatase that reverses mitotic Cdk1 phosphorylation. Despite evolutionary conservation, Clp1 's mammalian orthologs do not share this function. Rather, higher eukaryotic Cdc14 enzymes act in DNA repair, ciliogenesis, and gene regulation. To examine if Clp1 regulates gene expression, we compared the transcriptional profiles of cells lacking Clp1 function to that of wildtype. Because clp1∆ cells are sensitive to the actin depolymerizing drug, LatrunculinA, we also investigated whether a transcriptional response was involved. Our results indicate that Clp1 does not detectably affect gene expression and highlight the organism-specific functions of this conserved phosphatase family., Competing Interests: The authors declare that there are no conflicts of interest present., (Copyright: © 2024 by the authors.)

Background and Aims: Coronary flow capacity (CFC) is associated with an observed 10-year survival probability for individual patients before and after actual revascularization for comparison to virtual hypothetical ideal complete revascularization., Methods: Stress myocardial perfusion (mL/min/g) and coronary flow reserve (CFR) per pixel were quantified in 6979 coronary artery disease (CAD) subjects using Rb-82 positron emission tomography (PET) for CFC maps of artery-specific size-severity abnormalities expressed as percent left ventricle with prospective follow-up to define survival probability per-decade as fraction of 1.0., Results: Severely reduced CFC in 6979 subjects predicted low survival probability that improved by 42% after revascularization compared with no revascularization for comparable severity (P = .0015). For 283 pre-and-post-procedure PET pairs, severely reduced regional CFC-associated survival probability improved heterogeneously after revascularization (P < .001), more so after bypass surgery than percutaneous coronary interventions (P < .001) but normalized in only 5.7%; non-severe baseline CFC or survival probability did not improve compared with severe CFC (P = .00001). Observed CFC-associated survival probability after actual revascularization was lower than virtual ideal hypothetical complete post-revascularization survival probability due to residual CAD or failed revascularization (P < .001) unrelated to gender or microvascular dysfunction. Severely reduced CFC in 2552 post-revascularization subjects associated with low survival probability also improved after repeat revascularization compared with no repeat procedures (P = .025)., Conclusions: Severely reduced CFC and associated observed survival probability improved after first and repeat revascularization compared with no revascularization for comparable CFC severity. Non-severe CFC showed no benefit. Discordance between observed actual and virtual hypothetical post-revascularization survival probability revealed residual CAD or failed revascularization., (© The Author(s) 2023. Published by Oxford University Press on behalf of the European Society of Cardiology.)

Phosphatidylinositol (PI)-4-phosphate (PI4P) is a lipid found at the plasma membrane (PM) and Golgi in cells from yeast to humans. PI4P is generated from PI by PI4-kinases and can be converted into PI-4,5-bisphosphate [PI(4,5)P2]. Schizosaccharomyces pombe have two essential PI4-kinases - Stt4 and Pik1. Stt4 localizes to the PM, and its loss from the PM results in a decrease of PM PI4P and PI(4,5)P2. As a result, cells divide non-medially due to disrupted cytokinetic ring-PM anchoring. However, the localization and function of S. pombe Pik1 has not been thoroughly examined. Here, we found that Pik1 localizes exclusively to the trans-Golgi and is required for Golgi PI4P production. We determined that Ncs1 regulates Pik1, but unlike in other organisms, it is not required for Pik1 Golgi localization. When Pik1 function was disrupted, PM PI4P but not PI(4,5)P2 levels were reduced, a major difference compared with Stt4. We conclude that Stt4 is the chief enzyme responsible for producing the PI4P that generates PI(4,5)P2. Also, that cells with disrupted Pik1 do not divide asymmetrically highlights the specific importance of PM PI(4,5)P2 for cytokinetic ring-PM anchoring., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2023. Published by The Company of Biologists Ltd.)

Standardized nomenclature for genes, gene products, and isoforms is crucial to prevent ambiguity and enable clear communication of scientific data, facilitating efficient biocuration and data sharing. Standardized genotype nomenclature, which describes alleles present in a specific strain that differ from those in the wild-type reference strain, is equally essential to maximize research impact and ensure that results linking genotypes to phenotypes are Findable, Accessible, Interoperable, and Reusable (FAIR). In this publication, we extend the fission yeast clade gene nomenclature guidelines to support the curation efforts at PomBase (www.pombase.org), the Schizosaccharomyces pombe Model Organism Database. This update introduces nomenclature guidelines for noncoding RNA genes, following those set forth by the Human Genome Organisation Gene Nomenclature Committee. Additionally, we provide a significant update to the allele and genotype nomenclature guidelines originally published in 1987, to standardize the diverse range of genetic modifications enabled by the fission yeast genetic toolbox. These updated guidelines reflect a community consensus between numerous fission yeast researchers. Adoption of these rules will improve consistency in gene and genotype nomenclature, and facilitate machine-readability and automated entity recognition of fission yeast genes and alleles in publications or datasets. In conclusion, our updated guidelines provide a valuable resource for the fission yeast research community, promoting consistency, clarity, and FAIRness in genetic data sharing and interpretation., Competing Interests: Conflicts of interest statement The author(s) declare no conflict of interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of The Genetics Society of America.)

Biomedical sciences PhDs pursue a wide range of careers inside and outside academia. However, there is little data regarding how career interests of PhD students relate to the decision to pursue postdoctoral training or to their eventual career outcomes. Here, we present the career goals and career outcomes of 1452 biomedical sciences PhDs who graduated from Vanderbilt University between 1997 and 2021. We categorized careers using an expanded three-tiered taxonomy and flags that delineate key career milestones. We also analyzed career goal changes between matriculation and doctoral defense, and the reasons why students became more- or less-interested in research-intensive faculty careers. We linked students' career goal at doctoral defense to whether they did a postdoc, the duration of time between doctoral defense and the first non-training position, the career area of the first non-training position, and the career area of the job at 10 years after graduation. Finally, we followed individual careers for 10 years after graduation to characterize movement between different career areas over time. We found that most students changed their career goal during graduate school, declining numbers of alumni pursued postdoctoral training, many alumni entered first non-training positions in a different career area than their goal at doctoral defense, and the career area of the first non-training position was a good indicator of the job that alumni held 10 years after graduation. Our findings emphasize that students need a wide range of career development opportunities and career mentoring during graduate school to prepare them for futures in research and research-related professions., Competing Interests: The authors declare no conflicts of interest., (©2023 The Authors FASEB BioAdvances published by The Federation of American Societies for Experimental Biology.)

Coupling cell wall expansion with cell growth is a universal challenge faced by walled organisms. Mutations in Schizosaccharomyces pombe css1, which encodes a PM inositol phosphosphingolipid phospholipase C, prevent cell wall expansion but not synthesis of cell wall material. To probe how Css1 modulates cell wall formation we used classical and chemical genetics coupled with quantitative mass spectrometry. We found that elevated levels of the sphingolipid biosynthetic pathway's final product, mannosylinositol phosphorylceramide (MIPC), specifically correlated with the css1-3 phenotype. We also found that an apparent indicator of sphingolipids and a sterol biosensor accumulated at the cytosolic face of the PM at cell tips and the division site of css1-3 cells and, in accord, the PM in css1-3 was less dynamic than in wildtype cells. Interestingly, disrupting the protein glycosylation machinery recapitulated the css1-3 phenotype and led us to investigate Ghs2, a glycosylated PM protein predicted to modify cell wall material. Disrupting Ghs2 function led to aberrant cell wall material accumulation suggesting Ghs2 is dysfunctional in css1-3. We conclude that preventing an excess of MIPC in the S. pombe PM is critical to the function of key PM-localized proteins necessary for coupling growth with cell wall formation., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Willet et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Myosin-1s are monomeric actin-based motors that function at membranes. Myo1 is the single myosin-1 isoform in Schizosaccharomyces pombe that works redundantly with Wsp1-Vrp1 to activate the Arp2/3 complex for endocytosis. Here, we identified Ank1 as an uncharacterized cytoplasmic Myo1 binding partner. We found that in ank1Δ cells, Myo1 dramatically redistributed from endocytic patches to decorate the entire plasma membrane and endocytosis was defective. Biochemical analysis and structural predictions suggested that the Ank1 ankyrin repeats bind the Myo1 lever arm and the Ank1 acidic tail binds the Myo1 TH1 domain to prevent TH1-dependent Myo1 membrane binding. Indeed, Ank1 overexpression precluded Myo1 membrane localization and recombinant Ank1 reduced purified Myo1 liposome binding in vitro. Based on biochemical and cell biological analyses, we propose budding yeast Ank1 and human OSTF1 are functional Ank1 orthologs and that cytoplasmic sequestration by small ankyrin repeat proteins is a conserved mechanism regulating myosin-1s in endocytosis.

The Schizosaccharomyces pombe F-BAR protein, Cdc15, facilitates the linkage between the cytokinetic ring and the plasma membrane. Cdc15 is phosphorylated on many sites by four polarity kinases and this antagonizes membrane interaction. Dephosphorylation of Cdc15 during mitosis induces its phase separation, allowing oligomerization, membrane association, and protein partner binding. Here, using live cell imaging we examined whether spatial separation of Cdc15 from its four identified kinases potentially explains their diverse effects on tip septation and the mitotic Cdc15 phosphorylation state. We identified a correlation between kinase localization and their ability to antagonize Cdc15 cytokinetic ring and membrane localization., Competing Interests: The authors declare that there are no conflicts of interest present., (Copyright: © 2023 by the authors.)