Somatostatin (SST) is a multifunctional peptide and its function including its biosynthesis, posttranslational processing, gene regulation, regulation of secretion, islet and hypothalamic somatostatin function, somatostatin metabolism, receptors, and somatostatin dysfunction in disease such as diabetes, cancer, and neurodegeneration. This proposal is the continuation of 4 separate projects dealing with processing of SST, structure and function of somatostatin receptors (SSTR), role of SST in neurodegeneration and functional interaction of SSTRs with receptor tyrosine kinases. SST exists in two isoforms SST-14 and SST-28, derived from the same precursor Pro-SST. Our efforts in this direction are to define the molecular mechanism involved in the processing of Pro-SST to SST and elucidate whether there is any sorting receptor involve in SST maturation. Since the biological effect of SST is mediated by five different receptors subtypes namely SSTR1-5 member of G-protein coupled receptor (GPCR), exhibited homo-and heterodimerization with enhanced signaling and distinct pharmacological properties than the native receptors. Consistent with these observations we would like to determine the functional consequences of SSTR heterodimerization. In the central nervous system SST function as neurotransmitter and neuromodulator. SST cellular content and SST positive neurons selectively preserved in Huntington’s disease and gradually decreased in Alzheimer’s disease. Accordingly, the role of individual SSTR subtypes in different model of neurodegenerative diseases will be determined. The use of SST analogs is clinically proven in the treatment of variety of tumor. In breast cancer decrease SSTR expression and Increased expression of epidermal growth factor receptors (EGFRs) is frequently seen. Here we would like to delineate the role of SST and SSTRs on EGF induced transactivation of EGFR and modulation of down stream signaling cascade.
Research Pillar: Biomedical
Wild-type Huntingtin’s pro-survival function: A potential role in Huntington’s disease pathogenesis and treatment
Huntington's Disease (HD) is an Inherited brain disorder affecting approximately 1 in 10,000 Canadians that causes progressive disability with an inexorable march towards death averaging 18 years after the onset of symptoms. There is currently no cure for HD and no known treatment that affects the age of onset or the progression of symptoms. The underlying genetic defect that causes HD is now known and the mutant HD gene produces an abnormal protein called huntingtin (htt) that damages brain cells. Many research groups around the world are studying how the abnormal htt protein kills cells, but the normal cellular function of htt is not well understood. This proposal is unique in that we will examine the protective role that the normal htt protein may play in the disease process of HD. We previously demonstrated that the normal htt protein has a pro-survival function in the brain and prevents various forms of brain cell death. Our proposed experiments will determine what specific regions of htt are required for this protective role, how protein modifications of htt affect this function, and we will test what effect modulating levels of normal htt have on the progression and development of HD. Based on our preliminary results, I hypothesize that altering the pro-survival function of htt will modulate the process of brain cell injury in HD. Mapping the critical pro-survival regions of htt, investigating the mechanisms by which this function is regulated, and understanding the downstream pathways by which htt modulates brain cell death may provide novel cellular therapeutic targets for HD and for neurodegenerative disorders in general.
Genetics of alopecia areata
Alopecia areata (AA) is a common autoimmune disease leading to extensive hair loss in men, women and children. About 640,000 Canadians (one out of 50) will develop AA. There is no cure, and treatment options are minimal. While, in general, the condition is not life threatening, hair loss can be psychologically devastating, particularly for women and children. Using a rat model, Dr. McElwee has identified several areas on chromosomes where genes coding for AA susceptibility are present. Now further work is required to determine the specific genes involved and what they do. Once these genes are identified in the rat model, the next step is a large scale study to identify corresponding genes in AA-affected humans. A more comprehensive understanding of the structure and function of these genes in comparison to corresponding genes in non-affected individuals will lead to a better understanding of how AA develops. In the long run, the goal is to explore the development of treatments which specifically target and ameliorate the affects of underlying genetic flaws that give rise to the disorder.
Novel strategies for treatment of PTEN deficient prostate cancer
Prostate cancer (PCa) is the second leading cause of cancer-related deaths in men of the Westernized world. While early stage disease is frequently curable with surgery or radiotherapy, limited treatment options are currently available for approximately one-third of patients who clinically present with locally advanced or metastatic disease resulting in a poor prognosis for patients with advanced disease. One treatment option that is currently being used for advanced PCa is a medical procedures designed to block androgenic steroids to induce death of prostate cancer since prostate cancer cells typically require these hormones for their growth and integrity. While this treatment is often effective with a response rate of up to 80%, within 1-3 years the tumours inevitably recur as hormone-refractory variants, a condition for which there is no current effective therapy. Thus if we are to have an impact on survival rates of patients with PCa, new therapeutic strategies are required for treating advanced disease. Up to 50% of advanced prostate cancers have acquired mutations in a gene called PTEN that essentially inactivated it. Inactivation of PTEN in prostate cancer is correlated with a poor prognosis. Loss or inactivation of this gene makes prostate cancer cells more resistant to different forms of therapy including chemo-, radiation and hormone-therapy. The development and progression of cancer is dependent on the deregulation of the intricate balance in the rates of cell growth and death. The proposed project addresses how loss of the PTEN gene confers cell with a survival advantage and resistance to therapies. Under ordinary conditions, PTEN keeps growth of normal cells in check by serving as a brake to inhibit cell growth. When PTEN is mutated in cancer, the brakes fail and this confers uncontrolled growth and increased resistance of the cancer cells to chemotherapy and hormone ablation therapy. My lab is actively working on how loss of PTEN protects prostate cancer cells from death signals and we are looking for different ways to block the effects of inactivating PTEN. Results of this study will be directly relevant to development of new therapies aimed at treating the subset of advanced prostate cancers that have lost PTEN.
Nervous System Regeneration and Repair: Lessons From the Olfactory System
The brain or central nervous system (CNS) is especially vulnerable to permanent injury and loss of function following stroke, trauma and seizure or the onset of genetic disorders such as Huntington or Parkinson disease costing billions of dollars in health care every year and long-term loss of productivity. Despite major advances in understanding of neural development in recent years, a major challenge facing neuroscientists today is how to use this knowledge to help direct repair and rebuild the CNS after it becomes damaged. Dr. Jane Roskams uses the mouse olfactory system (nose) to study CNS repair because cells in the system have a remarkable ability to remodel, repair and regenerate, compared to other regions of the CNS. Olfactory system repair is driven by two types of cells â one that replaces lost neurons (specialized olfactory stem cells) and another that guides these replacement cells to their target (olfactory glial cells). As part of the only team in the world focused on these complementary research areas, Dr. Roskams has developed a series of tools and approaches to determine which specific cells are activated to replace damaged neurons, and to test the signals that drive this activity. She is also working to determine the unique ways that these cells contribute to repair following spinal cord injury and stroke. While transplanting either of these types of cells into injured or damaged CNS tissue could help with repair. Dr. Roskamsâ work is focused on understanding how repair mechanisms work at the molecular level, with the goal of discovering if there are ways that injured cells might be manipulated into repairing themselves â a potential new way of addressing or preventing long-term CNS damage.
Apolipoproteins and Autoimmunity to Lipid Antigens
The immune system is designed to rid the body of infections and unwanted cells, such as tumor cells or virally infected cells. The decision to target a certain agent for elimination is made by recognizing that a component (antigen) of a bacteria or virally infected cell is «foreign» to the body. Sometimes, however, the immune system can mistakenly target «self» components in healthy tissue, which leads to autoimmune diseases such as multiple sclerosis (MS). White blood cells called T cells are the central players in this decision making and are classically known to target protein components. Recently, however, it has been found that lipid components (ie. fats) can also be targeted by T cells, which is a new paradigm in immune recognition. We have been studying how T cells recognize lipids, and found that a major blood protein, apolipoprotein E (apoE), which was previously known to carry lipids for metabolic purposes, is also playing a role in the immune system to promote the recognition of lipids. ApoE has been known to play a role in many diseases, including MS and atherosclerosis (the disease of blood vessels which leads to heart disease and strokes). These two diseases also share common features in that there is immune system involvement which causes harm, in MS directed against the fatty insulation of nerves (myelin), and in atherosclerosis, immunity against unknown agents, possibly lipids found circulating in the blood. Our findings integrating lipid metabolism by apoE and the immune system thus open up a new area of research of direct relevance to MS and atherosclerosis, and we will set out to demonstrate that lipids are targeted in these diseases, and how apoE is involved to promote this mistaken targeting. Understanding these mechanisms will allow us to better monitor these disease using blood samples from patients, and also point to new strategies to treat disease by dampening or altering the immune response to lipids.
Mechanisms of X-linked Dyskeratosis congenita
Dyskeratosis congenita (DC) is an inherited premature-aging syndrome that typically results in bone-marrow failure. Symptoms include abnormal skin pigmentation, abnormal or absent nails and white, pre-cancerous areas on the lips and in the eyes, mouth and other body openings. More than 80% of patients with DC develop bone-marrow failure, which leads to decreased production of all types of blood cells. Premature death is usually the result of bone marrow failure. Most cases of DC are caused by changes in the DKC1 gene on the X chromosome. DKC1 encodes a protein called dyskerin, which helps maintains chromosomes, in addition to its essential function of manufacturing protein synthesis machinery. A symptom-free mother carrying a DKC1 mutation has a 50% chance of transmitting it to a son who will develop the disease.
Using genetic and biochemical techniques, Dr. Judy Wong is working to determine the mechanisms of X-linked DC. There are more than thirty amino acid mutations of the dyskerin protein that are known to be associated with X-linked DC. Understanding the molecular events that give rise to X-linked DC will help predict how patients will be affected and assist in the development of genetic therapies. Dr. Wong plans to test the effectiveness of dyskerin gene replacement techniques in restoring normal activity in X-linked DC cells. Her work will also improve our understanding of how other physiological factors can compromise normal aging.
The affects of Mgat5 modified glycoproteins and galectin-3 on the expression, phosphorylation and function of connexins
Cells in the human body are not isolated entities; in fact, they engage in a considerable amount of âcross talkâ with other nearby cells. In the most direct form of communication, protein channels pass through the membranes around neighboring cell, allowing small molecules to pass back and forth. These channels, called âgap junctionsâ, are made up of proteins called âconnexins.â Of interest to researchers is the discovery that production of connexins is reduced in aggressive cancers compared to the surrounding tissue. It is due to observations such as this which has led scientists to believe that connexins do more than just form âtunnelsâ between cells. Stephen Bond is examining the link between connexin 43, the most common form of connexin, and an enzyme called Mgat5. Too much Mgat5 encourages tumour growth, and âknocking outâ this enzyme (making it inoperative) increases the amount of connexin 43 protein made. Bond wants to determine whether an increase in Mgat5 increases tumour growth by decreasing connexin 43, and if so, determine how this occurs. This research could identify yet another way in which cells become cancerous, thus increasing our understanding of this class of disease, and hopefully lead to more effective treatments for cancer patients in the future.
Evaluating the contribution of bone micro-architecture, density and bone strength to fracture at clinically relevant sites using a novel instrument:An Xtreme CT study
Osteoporosis is a chronic condition whereby bones become fragile and individuals are predisposed to fracture. Osteoporosis may occur in all older people but it most frequently affects post-menopausal women. Worldwide, more than nine million osteoporosis-related fractures occur annually. Older Canadians sustain more than 24,000 hip fractures annually — which levies a substantial physical, emotional and economic burden on individuals and the health care system. By 2040, this number is expected to increase to 90,000 at a cost of $2.4 billion. The likelihood of a person sustaining a fracture is related to their bone strength and their propensity to fall. Bone strength is related to boneâs material and structural properties. Currently, DXA (dual-energy x-ray absorptiometry) is the most commonly used diagnostic tool to measure bone health. However this technology has limitations in that it provides a two-dimensional (2-D) representation of bone, a 3-D structure. Further, DXA does not capture the nuances of bone geometry and structure that underpin bone strength. Recently, a high resolution imaging system (the Xtreme CT scanner) was developed that is able to assess bone mass, geometry and bone microarchitecture. The extent to which this novel technology is able to predict bone failure is currently unknown. Thus, Sarah Braid will utilize state-of-the-art imaging techniques (X-treme CT and pQCT) to evaluate bone strength and its components â and most importantly – link these evaluative tools with the susceptibility of a bone to fracture. The results of her research will enhance our ability to assess fracture risk so as to prevent fractures in vulnerable populations in future.
Identification of microRNAs, their targets and roles in human embryonic stem cells
Stem cells are a special variety of cells that can self-renew indefinitely and can become a multitude of cell types. Embryonic stem cells are the most versatile variety of stem cells and can potentially develop into any adult cell type. Many cancer researchers believe that in most (if not all) types of cancers, there is a population of cancer stem cells that actively sustain the production of cancer cells. A better understanding of stem cells is crucial in advancing knowledge of all cell types, including cancer cells. Before manipulation of embryonic stem cells can be explored as a method of treating disease, and before anti-cancer drugs that target cancer stem cells can be designed, there is a need to understand the genetic structure and the signaling pathways that maintain these cells. Ryan Morinâs research is directed at understanding how the regulation of gene expression differs between embryonic stem cells during their differentiation into other cell types. His particular focus applies new sequencing technologies to unravel the cellular complexity of the regulatory molecules known as microRNAs and their involvement in embryonic stem cell gene regulation.