Biology subjects

Gholkar, A. A.

Publications and source records attributed to Gholkar, A. A..

4 recordsLinked to original sources

bioRxiv2020

DUSP7 Regulates the Activity of ERK2 to PromoteProper Chromosome Alignment During Cell Division

Human cell division is a highly regulated process that relies on the accurate capture and movement of chromosomes to the metaphase plate. Errors in the fidelity of chromosome congression and alignment can lead to improper chromosome segregation, which is correlated with aneuploidy and tumorigenesis. Here we show that the dual specificity phosphatase DUSP7 is important for regulating chromosome alignment. DUSP7 bound to ERK2 and regulated the abundance of active phospho-ERK2 through its phosphatase activity. Overexpression of DUSP7, but not catalytic dead mutants, led to a marked decrease in phopho-ERK2 and mitotic chromosome misalignment, while knockdown of DUSP7 also led to defective chromosome congression that resulted in a prolonged mitosis. Consistently, chemical inhibition of the MEK kinase that phosphorylates ERK2 or ERK2 itself led to chromosome alignment defects. Our results support a model where MEK phosphorylation and DUSP7 dephosphorylation regulate the levels of active phospho-ERK2 to promote proper cell division.

cell biology↗

bioRxiv2020

Regulation of Iron Homeostasis Through Parkin-mediated Lactoferrin Ubiquitylation

Somatic mutations that perturb Parkin ubiquitin ligase activity and the misregulation of iron homeostasis have both been linked to Parkinsons disease. Lactotransferrin is a member of the transferrin iron binding proteins that regulate iron homeostasis and increased levels of Lactotransferrin and its receptor have been observed in neurodegenerative disorders like Parkinsons disease. Here, we report that Parkin binds to Lactotransferrin and ubiquitylates it to regulate iron homeostasis.

biochemistry↗

bioRxiv2020

Dissection of the Spindle Assembly Checkpoint by Proximity Proteomics

The spindle assembly checkpoint (SAC) is critical for sensing defective microtubule-kinetochore attachments and tension across the kinetochore and functions to arrest cells in prometaphase to allow time to repair any errors prior to proceeding into anaphase. The SAC has a central role in ensuring the fidelity of chromosome segregation and its dysregulation has been linked to the development of human diseases like cancer. The establishment and maintenance of the SAC relies on multiple protein complexes that are intricately regulated in a spatial and temporal manner through posttranslational modifications like phosphorylation. Over the past few decades the SAC has been highly investigated and much has been learned about its protein constituents and the pathways and factors that regulate its activity. However, the spatio-temporal proximity associations of the core SAC components have not been explored in a systematic manner. Here, we have taken a BioID2 proximity-labeling proteomic approach to define the proximity protein environment for each of the five core SAC proteins BUB1, BUB3, BUBR1, MAD1L1, and MAD2L1 under conditions where the SAC is active in prometaphase. These five protein association maps were integrated to generate the SAC proximity protein network that contains multiple layers of information related to core SAC protein complexes, protein-protein interactions, and proximity associations. Our analysis validated many of the known SAC complexes and protein-protein interactions. Additionally, it uncovered new protein associations that lend insight into the functioning of the SAC and highlighted future areas that should be investigated to generate a comprehensive understanding of the SAC.

biochemistry↗

bioRxiv2020

The myosin regulatory light chain Myl5 localizes to mitotic spindle poles and is required for proper cell division

Myosins are ATP-dependent actin-based molecular motors critical for diverse cellular processes like intracellular trafficking, cell motility and cell invasion. During cell division, myosin MYO10 is important for proper mitotic spindle assembly, the anchoring of the spindle to the cortex, and positioning of the spindle to the cell mid-plane, while myosin MYO2 functions in actomyosin ring contraction to promote cytokinesis. However, myosins are regulated by myosin regulatory light chains (RLCs), and whether RLCs are important for cell division has remained unexplored. Here, we have determined that the previously uncharacterized myosin RLC Myl5 associates with the mitotic spindle and is required for cell division. Myl5 localized to the mitotic spindle poles and spindle microtubules during early mitosis, an area overlapping with MYO10 localization. Depletion of Myl5 led to defects in chromosome congression and to a slower progression through mitosis. We propose that Myl5 is a novel myosin RLC that is important for cell division.

cell biology↗