Investigating the polyphosphate interactome with lysine- and histidine-rich proteins

Inorganic polyphosphate (polyP) is a biomolecule whose diverse functionality greatly belies its simple structure. PolyP is comprised of repeated inorganic phosphate units forming high energy phosphoanhydride linked polymers. Numerous studies have highlighted its vast portfolio of functions that manifest their effects in a wide range of physiological pathways, including proteostasis, hemostasis, and phagocytosis. In particular, this thesis focuses on a remarkable post-translational modification (PTM)-like function of polyP, featured by its strong but non-covalent interaction with lysine repeat proteins, termed lysine polyphosphate modification (KPM). Amidst studying histidine polyphosphate modifications (HPM), proteins with repeating lysine residues emerged as plausible polyP targets. Screening within yeast, human, and bacterial proteomes revealed 19 novel KPM target proteins. Much like HPM, KPM exhibits polyP-dependent electrophoretic shifts on NuPAGE gels. However, upon deletion or mutation of the lysine residues the mobility shift is abolished indicating that these modifications are lysine-dependent. Additionally, KPM is also considered ionic in nature due to its susceptibility to both ionic strength and pH fluctuations. We show that polyP modifications can modulate protein activity of several enzymes, including the oncogenic GTPase, K-Ras, as well as the ATP-dependent RNA helicase, DDX55. We also studied the non-canonical HPM target protein, histidine-rich glycoprotein (HRG) to which we uncovered that HPM reduced its ability to bind IgG1. Moreover, we demonstrate that S100A9, a known ligand of HRG, is prone to multimerization in the presence of polyP. Though the physiological relevance of both HPM and KPM remain unclear, we suggest that the polyP-protein interactome is involved in widespread regulatory mechanisms of protein homeostasis and human health.

Department dc:contributor.department

Biomedical and Molecular Sciences

Year dc:date.issued

2024

Author dc:creator

• Lehotsky, Kirsten

Advisor dc:contributor.supervisor

• Jia, Zongchao

• histidine repeats
• lysine repeats
• polyphosphate
• polyphosphate modification
• HRG
• K-Ras
• DDX55
• Pseudomonas aeruginosa
• PASK

Statement dc:rights

• Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1974/33460

OAI identifier oai:identifier

oai:queensu.scholaris.ca:1974/33460