Chad Slawson, PhD
Biochemistry and Molecular Biology
PhD, University of South Florida
To Understand the Regulation of the Post-Translational Modification O-GlcNAc During Mitosis
What is O-GlcNAc? O-GlcNAc is the addition of a single N-acetyl-glucosamine residue to serine/threonine residues of proteins found in the cytoplasm or nucleus (O-GlcNAcylation). Unlike extracellular glycosylation, the sugar residue is not elongated into complex oligosaccharides and is processed dynamically in response to cellular stimuli by a single O-GlcNAc transferase (OGT) or O-GlcNAcase (OGA). O-GlcNAc is involved in many cellular processes such as nutrient sensing, stress response, transcription, translation, cell signaling, and cell cycle regulation.
O-GlcNAc Regulates Mitosis! All dividing cells must undergo mitosis, the process in which a eukaryotic cell separates into two daughter cells containing identical sets of chromosomes surrounded by a newly formed nucleus while partitioning cellular components such as organelles and cytoplasm equally to the two daughter cells. This elaborate process is coordinated by hundreds of proteins, and many of these proteins is regulated by post-translational modifications. Notably, the phosphorylation of proteins by Cyclin Dependent Kinase 1 (CDK1) is one master switch to control mitotic progression. On the other hand, a large number of proteins are heavily modified by O-GlcNAc during mitosis. O-GlcNAcylation regulates the function, localization, degradation, and protein interactions of these proteins. Furthermore, the regulation of CDK1 is due to O-GlcNAcylation.
Anueploidy, when Mitosis goes Bad! Errors in the regulation of proteins during mitosis can give rise to aneuploidy, which is an abnormal number of chromosomes in the daughter cells. This phenotype is seen in diseases characterized by abnormal growth and proliferation such as cancer. Interestingly, elevations in the expression of OGT cause aneuploidy. This is partially due to the fact that OGT localizes to mitotic structures such as the spindle and midbody during mitosis and altered O-GlcNAcylation at these sites promote aneuploidy.
What's Next? Currently, we are asking several questions to understand how O-GlcNAc regulates mitosis such as how is OGT targeted to specific structures at M phase as well as to specific substrates? What is the dynamics of O-GlcNAcylation throughout mitosis? What mitotic signaling pathways are regulated by O-GlcNAcylation? In order to ask these questions my laboratory uses a variety of techniques from cloning, western blotting, imaging, and mass spectroscopy