Jagiellonian University

Ubiquitin-related modifier 1 (Urm1) is known for its dual role as sulfur carrier protein (SCP) in tRNA thiolation and as an ubiquitin-like protein (UBL) that leads to an oxidant-induced posttranslational protein modification (PTM). We recently, managed to recapitulate the Urm1-conjugation reaction for various targets in vitro and characterize the underlying molecular principles. In most ubiquitin (Ub) and ubiquitin-like- conjugation systems, the active removal of the PTM constitutes a key feature of the regulatory mechanisms. Although, various targets of urmylation have been reported, not a single enzyme that could reverse the modification has been identified. In this project, I plan to incorporate different complementary discovery strategies to ultimately identify possible “deurmylation” enzymes in yeast and human and assess their biological significance. Foremost, I aim to uncover the guiding principles that regulate the evolutionary most ancient UBL system in eukaryotes. Hence, the expected results will not only answer one of the most intriguing questions related to Urm1, but have far-reaching consequences for our understanding of all UBL systems in eukaryotes. Last but not least, several studies hint at the critical function of Urm1 conjugation in oxidative stress response and at its direct involvement in severe human diseases. As various deubiquitylating enzymes (DUBs) are successfully developed as potent targets for small-molecule based drug therapies, the identified enzyme(s) could be well suited for novel therapeutic and diagnostic strategies.

Ageing is recognized as one of the greatest social and economical challenges of the 21century for European societies. With, Vascular Cognitive Impairment (VCI) being one of the leading causes of age-related cognitive impairment and one of the major causes of disability in the elderly. Although, the concept of VCI was introduced in 1993, current treatment is limited to management of vascular risks and symptomatic pharmacotherapy targeting vascular dementia. The overall objective of this project is to fill the significant gap in early detection, prevention and treatment of VCI. This will be achieved by explaining microvascular mechanism of protective effects of thrombopoietin (TPO) in a novel unique mixed-risk animal model of VCI- specific to hypertension plus carotid-artery hypoperfusion (HH-VCI). Given increased number of progenitor endothelial cells after TPO treatment, it is hypothesizes that protective effect of TPO is mediated by endothelium. Furthermore, protective effect of TPO is expected to be caused by activation of neoangiogenesis, anti-inflammatory and vasoprotective mechanisms driven by TPO action on endothelial. This hypothesis will be tested in two stages first, in-vitro and second, in-vivo. In-vitro models, will be used to investigate endothelial response to TPO in terms of its modulation of inflammatory response angiogenic potential and vasoprotective mechanisms. In-vivo models of TPOR KO mice and HH-VCI mice will be used to validate and confirm mechanisms identified in in vitro stage of experiments.

Animals and microbes interact in intricate ways. Wolbachia, a common intracellular insect symbiont, can manipulate reproduction and protect hosts from viruses. Thus, Wolbachia is an asset in the control of insect-borne diseases. However, as Wolbachia cannot be cultured outside of host cells or genetically manipulated, the mechanisms of its antiviral phenotype remain poorly understood, and this inhibits wider exploitation. I have been working to remedy these deficiencies, and now stand poised to discover the mechanisms of Wolbachia-conferred antiviral protection by answering the following questions: 1) Where does the protection originate? Up to now, mechanisms of protection have been studied in whole organisms, often lacking resolution, or in cultured cells, which lack emergent properties. I will identify tissues and cell types of the host where protection starts. To do this, I will: a) quantify titers of Wolbachia and virus at early time points post-viral infection in insect tissues, b) measure gene expression of host and microbes to identify candidates for further molecular characterisation, and c) test the extent of the utility of widely adopted, yet unvalidated, cell-culture models of antiviral protection. 2) Which Wolbachia genes effect protection? Wolbachia research has historically been impeded by a lack of tools to study gene function. Here, I will deploy antisense technology, which I have recently developed, to interrogate function of candidate Wolbachia genes in the native system. I will also engineer new methods to target Wolbachia genes and proteins, based on my data on cell-penetrating peptide-mediated delivery of bioactive cargo to Wolbachia. This project has two major outcomes: it will uncover Wolbachia factors responsible for Wolbachia-conferred antiviral protection, and it will transform Wolbachia and symbiosis research by creating tools to study symbiont gene function.

Human organism produces over a million new blood cells each second. The hematopoietic system dynamically reacts to environmental stress and forms adaptive immunity to memorize and effectively fight the encounter pathogens. However, based on our recent studies and preliminary results, we propose that the adaptive capabilities and memory of the hematopoietic system reach far beyond the classical adaptive antigen-specific immunity. We hypothesize that hematopoietic stress induces clonal expansion of lineage-biased hematopoietic stem cells (HSCs) with epigenetic memory that faster and more effectively respond to secondary stimulation with a given stress factor. We propose that lineage-biased HSCs accumulating during aging provide a broad adaptive memory of the hematopoietic system, that is not restricted to immune cells, but includes all blood cell lineages. The aim of our proposal is to understand how the HSC-stored memory is created, maintained and recalled, and to clarify the underlying mechanisms. First, we will selectively stimulate granulopoiesis, erythropoiesis and thrombopoiesis to define the specificity and physiological role of hematopoietic memory provided by HSCs, both in vitro and in vivo. Second, we will use single-cell level fate mapping and sequencing to investigate clonal and epigenetic mechanisms driving the HSCs-based memory in mice. Third, we will test if aging pool of human HSCs consists of lineage-biased HSCs that store memory of the previously encountered stimuli. The humanized mice models will determine the clonal expansion of human HSCs upon primary and secondary stimulation with stress factors. Altogether, the expected outcome of the project is to understand how and why hematopoietic system adjusts to the environmental challenges upon aging. The proposed novel concept of the hematopoietic system adaptivity may help to design strategies to train patients' hematopoiesis and improve the transplantations of HSCs.