Biology subjects

Fonseca, C. L.

Publications and source records attributed to Fonseca, C. L..

3 recordsLinked to original sources

bioRxiv2026

A Phosphorylation Switch Governs KIF11's Mechanical Output During Mitosis

The kinesin-5 motor protein KIF11 is crucial for mitotic spindle assembly, driving the separation of spindle poles through microtubule sliding. Src-family kinases phosphorylate KIF11 at multiple tyrosine residues within its motor domain, but the mechanistic consequences of these modifications remain unclear. Here, we dissect the role of phosphorylation at Y211 using phospho-mimetic (Y211E) and non-phosphorylatable mutants (Y211F) in biochemical, biophysical, and cellular assays. Optical trapping and Forster resonance energy transfer (FRET) analyses reveal that Y211 phosphorylation slows neck-linker docking, reducing motor velocity and force generation under load. In human cells, Y211E expression impairs bipolar spindle formation and decreases spindle pole separation velocity, while Y211F shortens steady-state spindle length. Fluorescence recovery after photobleaching (FRAP) analyses show that Y211E accelerates motor turnover on spindle microtubules, consistent with the mutant motors heightened load sensitivity. Together, these findings support a model in which Src-mediated phosphorylation at Y211 acts as a rheostat to tune KIF11 mechanochemistry and spindle assembly dynamics, linking cancer-relevant kinase signaling to mitotic force generation.

cell biology↗

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↗

bioRxiv2018

Mitotic chromosome alignment is required for proper nuclear envelope reassembly

Chromosome alignment at the equator of the mitotic spindle is a highly conserved step during cell division, however, its importance to genomic stability and cellular fitness are not understood. Normal mammalian somatic cells lacking Kif18A function complete cell division without aligning chromosomes. These alignment-deficient cells display normal chromosome copy numbers in vitro and in vivo, suggesting that chromosome alignment is largely dispensable for maintenance of euploidy. However, we find that loss of chromosome alignment leads to interchromosomal compaction defects during anaphase, abnormal organization of chromosomes into a single nucleus at mitotic exit, and the formation of micronuclei in vitro and in vivo. These defects slow cell proliferation and reduce postnatal growth and survival with variable penetrance in mice. Our studies support a model in which the alignment of mitotic chromosomes promotes proper nuclear envelope reassembly and continued proliferation by ensuring that chromosomes segregate as a compact mass during anaphase.

cell biology↗