Clayton, J. E. | Search bioRxiv

bioRxiv2020

Chromosomally unstable tumor cells specifically require KIF18A for proliferation

Chromosomal instability (CIN), characterized by frequent missegregation of chromosomes during mitosis, is a hallmark of tumor cells caused by changes in the dynamics and control of microtubules that comprise the mitotic spindle1-3. Thus, CIN tumor cells may respond differently than normal diploid cells to treatments that target mitotic spindle regulation. We tested this idea by inhibiting a subset of kinesin motor proteins that control spindle microtubule dynamics and mechanics but are not required for the proliferation of near-diploid cells. Our results indicated that KIF18A was required for proliferation of CIN cells derived from triple negative breast cancer or colorectal cancer tumors but was not required in near-diploid cells. CIN tumor cells exhibited mitotic delays, multipolar spindles due to centrosome fragmentation, and increased cell death following inhibition of KIF18A. Sensitivity to KIF18A knockdown was strongly correlated with centrosome fragmentation, which required dynamic microtubules but did not depend on bipolar spindle formation or mitotic arrest. Our results indicate the altered spindle microtubule dynamics characteristic of CIN tumor cells can be exploited to reduce the proliferative capacity of CIN cells.

cell biology↗

bioRxiv2019

Live-cell assays for cell stress responses reveal new patterns of cell signaling caused by mutations in rhodopsin, α-synuclein and TDP-43

Many neurodegenerative diseases induce high levels of sustained cellular stress and alter a number of cellular processes. Genetically-encoded fluorescent biosensors are effective tools to examine neuronal activity and signaling in living cells. To examine how different mutations associated with neurodegenerative disease affect cell stress and signaling we created live-cell assays for ER-mediated cell stress and second messenger signaling. Analysis of the rhodopsin P23H mutation, the most common mutation in autosomal dominant Retinitis Pigmentosa, revealed increased cell stress levels compared to wild type rhodopsin. Moreover, this increase in cell stress correlated with blunted Ca2+ signaling in a stress dependent manner. Analysis of single cell Ca2+ signaling profiles revealed unique Ca2+ signaling responses exist in cells expressing wild type or P23H mutants, further supporting the notion that second messenger signaling is affected by cell stress. To explore the use of the ER-stress biosensor in other neurodegenerative diseases we examined how various mutants of -synuclein and TDP-43 affected ER-mediated cell stress. Mutants of both -synuclein and TDP-43 associated with Parkinsons Disease and ALS demonstrated increases in ER-mediated cell stress. This increased cell stress was accompanied by changes in phosphodiesterase activity. Both HEK293T and SH-SY5Y cells expressing these proteins displayed a shift towards increased cAMP degradation rates, likely due to increased phosphodiesterase activity. Together these data illustrate how biosensors can provide nuanced, new views of neurodegenerative disease processes.

neuroscience↗