Biology subjects

Starling, G. P.

Publications and source records attributed to Starling, G. P..

4 recordsLinked to original sources

bioRxiv2024

The ALS- and FTD-associated proteins Annexin A11 and CHMP2B act sequentially in membrane repair

Maintenance of plasma membrane and organellar integrity is essential for cell viability. Cells must recognise damaged membranes and orchestrate repair programmes to preserve compartmentalisation. A variety of cellular factors including ESCRTs, Annexins, stress granules, lipids and proteins allowing vesicle and organelle fusion with damaged membranes have been reported to contribute to membrane repair. However, whether these factors operate independently or together to repair membranes is unclear. Here, we expose temporal differences and interdependencies in the recruitment of ESCRT-III and Annexin proteins to sites of membrane damage. We show that while Annexins are recruited immediately to sites of damage, ESCRT-III assembles only after membrane sealing. We show that ESCRT-III acts to shed damaged membranes from the cell and that FTD-and ALS-associated mutations in CHMP2B and ANXA11 compromise the repair process. These data present an integrated sealing and healing model of events allowing membrane repair and restoration of membrane integrity. One-Sentence Summary: A rubric of sealing and healing for ESCRT-mediated membrane repair

cell biology↗

bioRxiv2022

Katnip is required to maintain microtubule function and lysosomal delivery to autophagosomes and phagosomes

The efficient delivery of lysosomes is essential for many cell functions, such as the degradation of unwanted intracellular components by autophagy and the killing and digestion of extracellular microbes within phagosomes. Using the amoeba Dictyostelium discoideum we find that cells lacking Katnip (Katanin interacting protein) have a general defect in lysosome delivery and whilst able to make autophagosomes and phagosomes correctly are then unable to digest them. Katnip is largely unstudied yet highly conserved across evolution. Previously studies found Katnip mutations in animals cause defects in cilia structure. Here we show that Katnip plays a general role in maintaining microtubule function. We find that loss of Katnip has no overall effect on microtubule dynamics or organisation, but is important for the transport and degradation of endocytic cargos. Strikingly, Katnip mutants become highly sensitive to GFP-tubulin expression, which leads to microtubule tangles, defective anaphase extension and slow growth. Our findings establish a conserved role for Katnip in the function of all microtubules, not just cilia as previously reported. We speculate this is via a key function in microtubule repair, required to maintain endosomal trafficking and lysosomal degradation.

cell biology↗

bioRxiv2021

Endomembranes promote chromosome missegregation by ensheathing misaligned chromosomes

Errors in mitosis that cause chromosome missegregation lead to aneuploidy and micronuclei formation which are associated with cancer. Accurate segregation requires the alignment of all chromosomes by the mitotic spindle at the metaphase plate, and any misalignment must be corrected before anaphase is triggered. The spindle is situated in a membrane-free "exclusion zone", beyond this zone, endomembranes (endoplasmic reticulum, nuclear envelope and other organelles) are densely packed. We asked what happens to misaligned chromosomes that find themselves beyond the exclusion zone? Here we show that such chromosomes become ensheathed in multiple layers of endomembranes. Chromosome ensheathing delays mitosis and increases the frequency of chromosome missegregation. The micronuclei that form following missegregation have a disrupted nuclear envelope with internal endomembranes. We use an induced organelle relocalization strategy in live cells to show that clearance of endomembranes allows for the rescue of chromosomes that were destined for missegregation. Our findings indicate that endomembranes promote the missegregation of misaligned chromosomes that are outside the exclusion zone, and therefore constitute a risk factor for aneuploidy.

cell biology↗

bioRxiv2016

Microtubule organization within mitotic spindles revealed by serial block face scanning EM and image analysis

Serial block face scanning electron microscopy (SBF-SEM) is a powerful method to analyze cells in 3D. Here, working at the resolution limit of the method, we describe a correlative light-SBF-SEM workflow to resolve microtubules of the mitotic spindle in human cells. We present three examples of uses for this workflow which are not practical by light microscopy and/or TEM. First, distinguishing closely associated microtubules within K-fibers; second, resolving bridging fibers in the mitotic spindle; third, visualizing membranes in mitotic cells, relative to the spindle apparatus. Our workflow also includes new computational tools for exploring the spatial arrangement of MTs within the mitotic spindle. We use these tools to show that microtubule order in mitotic spindles is sensitive to the level of TACC3 on the spindle.

cell biology↗