A heart that has become enlarged in response to a pressure overload, such as with high blood pressure, has reduced function compared to a normal heart. This impaired function is particularly apparent during and after interruption of the blood supply, which can occur when a blood clot blocks a diseased coronary artery, or during open heart surgery. This reduced heart function can be very dangerous for the patient. Enlarged hearts use glucose to a greater extent than normal, a situation that appears to contribute to their exaggerated dysfunction. The mechanisms responsible for the accelerated utilization of glucose in enlarged hearts are not yet known. Dr. Minnie Dai was previously funded by MSFHR for her doctoral training. Currently, she is working to determine the mechanisms behind accelerated rates of glucose utilization in enlarged hearts. Using molecular biology techniques, she will selectively and specifically alter the activity of potentially relevant proteins in order to determine their role in causing accelerated glucose utilization. Her studies are unique in that the activity of proteins will be altered at specific times and will be altered only in the heart – ensuring that changes observed are truly related to alterations in these proteins. Many people suffer ill health because of an enlarged heart. By understanding the mechanisms responsible for their accelerated use of glucose, researchers may be able to identify targets for the development of drugs designed to altered glucose use by enlarged hearts, thereby improving their function.
Research Pillar: Biomedical
Proteomics of natural substrates of PMN and macrophage proteases in inflammation
Chronic obstructive pulmonary disease (COPD) is a serious lung disease that is predicted to become the fifth leading cause of death by 2020. It is marked by inflammation of the airways. Currently, there is no efficient drug for treatment for this disease. A promising area of COPD research is focused on matrix metalloproteases (MMP), a family of proteins that digest or cut other proteins (known as substrates) into smaller pieces. These cleavages modify the biological functions of the substrate. MMPs are implicated in many inflammatory diseases, including COPD. Dr. Alain Doucet is studying how two specific MMPs, MMP-8 and MMP-12, contribute to the development of COPD. He is conducting studies to validate his hypothesis that MMP-8 and -12 regulate inflammation by cleaving immune cell mediators such as cytokines, chemokines and their cellular receptors. He is conducting a proteomic identification of MMP-8 and -12 biological substrates and assessing the effect of the substrate cleavage on its biological activity. This work could lead to identification of new, more refined targets for COPD treatment. The identification of MMP-8 and -12 biological substrates will indicate their cleavage specificity and will help in the design of more specific inhibitors. Anti-inflammatory drugs developed for COPD treatment also have the potential to be applied to other inflammatory-associated diseases, such as cancer and arthritis.
Wnt signalling during avian facial morphogenesis
It is estimated that 1 in 800 babies is born with cleft lip with or without a cleft palate, making CL/P the most common craniofacial malformation in humans. The lip forms during the early embryonic period in utero, at which time the face is very different from its appearance after birth. Initially, there are separate swellings that surround the oral cavity, several of which grow together and fuse in order to make a continuous smooth upper lip. Dr. Poongodi Geetha-Loganathan is determining the molecules that are required for normal lip fusion, focusing the roles of Wnt genes in the control of facial growth. She is using chickens as a model for facial development, observing through windows made in the shell how the beak develops, and the role of different proteins or DNA. This work will help researchers find those changes in genes that give rise to clefts. In the long term these discoveries will lead to identification of new genes that cause human orofacial clefts, potentially suggesting ways to prevent this common birth defect.
Dissection of O-glycosylation of nuclear and cytoplasmic proteins
The recent decoding of the human genome surprisingly revealed that humans possess a relatively small number of genes. Yet despite this apparently small number, we are rather complex beings. Genes are a special code that can be read out to form proteins, which are responsible for the vast majority of biochemical process within our bodies. This apparent inconsistency between the number of genes and the complexity of humans can be, in part, accounted for by various ‘post-translational modifications’ of human proteins. These types of modification are often additional molecule groups that are added onto certain positions in the protein and can change its activity. Dr. Tracey Gloster is interested in a modification where there is addition and removal of a sugar called ‘N-acetylglucosamine’. Disruptions to this modification are implicated in conditions such as diabetes, cancer and neurodegenerative diseases. The enzyme responsible for adding the N-acetylglucosamine modifies a large number of completely different target proteins. Little is known about how the enzyme recognizes its targets and modifies them at the correct position to ensure they carry out their proper function. Gloster is investigating a specific domain on this enzyme that could hold the answer. There are multiple sites on this interacting domain which she believes each recognize different sets of target proteins. By finding proteins that are modified by this protein and determining the exact region of the target protein that binds to the enzyme, it may be possible to block the enzyme’s action. This could open up new therapeutic approaches in the treatment of diabetes and other diseases.
Immunomodulation of regulatory mechanisms in mucosal immunity
Inflammatory bowel diseases (IBD) are chronic conditions characterized by severe inflammation of parts of the bowel, causing significant symptoms, such as diarrhea, pain and intestinal bleeding. There are two main types of IBD: Crohn’s disease and ulcerative colitis. IBD is prevalent in Canada, with an estimated 170,000 people suffering from the disease. Despite years of effort, the causes of these disorders remain incompletely and inadequately understood. The intestinal inflammation in IBD is thought to result from abnormal responses to the bacteria that live normally in the gut. In healthy individuals, the immune system is able to distinguish between harmless (commensal) bacteria and those that cause infections (pathogens). In IBD patients, the immune system elicits an aberrant and aggressive response against components of host commensal bacteria. Dendritic cells (DC) and regulatory T cells (nTreg) are two types of cells important in maintaining a healthy intestinal immune system. Defects in the development or function of these cells could ultimately lead to inappropriate responses to commensal bacteria, or certain commensal bacteria or pathogens could perturb the normal immune state of the gut. Dr. Gijs Hardenberg is investigating the interplay between host commensal bacteria and the immune system in IBD. He is studying the roles of nTreg and immune responses, focusing on the bacterial protein flagellin, which has been shown to be the major target of intestinal immune responses in Crohn’s disease patients. His work aims to understand how IBD begins and persists how it might ultimately be treated or even prevented. The findings from these studies may also be broadly applicable to other autoimmune diseases such as rheumatoid arthritis, multiple sclerosis, and lupus.
Treating breast cancer with a novel programmable fusogenic gene delivery system for small interfering RNA targeting integrin-linked kinase
Cancer is a disease characterized by specific functional capabilities that are not typically expressed by normal healthy cells. For example, cancer cells can grow in the absence of normal growth signals, build resistance to the detrimental effects of drugs, invade and spread to other sites of the body. These capabilities are a result of acquired or inherited genetic mutations to DNA within cells, damaging genetic information that defines normal cellular function. If these unique features of cancer cells can be altered or corrected using gene therapy, it may provide an effective strategy to treat cancer. Studies have shown that in both plants and animal cells, introduction of man-made molecules known as small interfering RNAs (siRNA) can result in the suppression (silencing) of specific genes that promote cancer growth. Ultimately, this weakens the cancer cells to cause cell death or make cancer cells more vulnerable to radiation and/or chemotherapy. One promising siRNA treatment targets breast cancer by suppressing integrin-linked kinase (ILK), a protein that is known to be over-expressed in breast cancer. However, the effectiveness of siRNA treatment is currently hampered by issues related to the way the drug is delivered to the tumour. Dr. Emmanuel Ho is working to develop and test a novel method to deliver the drug only to cancer cells, leaving healthy, non-cancerous cells unaffected. By doing so, he hopes that the siRNA will decrease the expression of ILK and result in a decrease of breast tumour growth. If this new drug delivery system proves successful, the technology will enhance breast cancer treatment and facilitate the development of other siRNAs that are safe and effective.
Development of a novel prognostic model in Follicular Lymphoma
Lymphoid cancers are the fourth most common cancers in Canada. The incidence of follicular lymphoma (FL), a common and incurable subtype of lymphoma, continues to rise and represent an important health care problem. The prognosis for patients with FL can vary widely, from cases that spontaneously go into remission, to aggressive forms of FL where life expectancy is measured in months. Transformation of FL to a more aggressive transformed lymphoma (TLy) occurs in one third of the patients over 10 years and is an important cause of patient morbidity and mortality. With an enhanced ability to distinguish among different FL types and their prognoses, clinicians could safely delay treatment or give minimally toxic therapy to low risk patients, and reserve more aggressive chemotherapy to high risk patients. Dr. Nathalie Johnson is a hematologist working to improve clinical tools for identifying high risk FL patients. She is focusing on novel biomarkers that are associated with disease severity, identifying the most significant genetic factors in the tumour and in the patient that predict overall survival (OS) and transformation to Tly in FL. So far, she and her colleagues have found 85 genes that are highly predictive of survival and 55 genes that are predictive of transformation. Johnson will use this knowledge to develop and test a diagnostic model that can be translated into clinical tests for use by hospital laboratories. Her project seeks to move novel biomarkers into the forefront of outcome prediction, which will lead to individualized patient care and should identify novel targets for future therapies.
The role of ABC transporters on cellular cholesterol homeostasis and beta-cell function
Type 2 diabetes affects more than two million Canadians and causes a range of significant health issues, including coronary heart disease, the leading cause of death in Canada. Type 2 diabetes results from a relative insufficiency of beta-cells in the pancreas to produce enough insulin to meet the increasing metabolic demands caused by obesity and aging. Cholesterol levels among type 2 diabetes patients is also known to commonly be altered, with elevated levels of LDL (“bad cholesterol”) and low levels of HDL (“good cholesterol”). However, the mechanistic connections between cholesterol metabolism and diabetes are poorly understood. Researchers recently discovered that the cholesterol transporter ABCA1, which is crucial for regulating cholesterol levels inside cells, is also essential for the normal release of insulin in beta-cells. Mice that lack Abca1 in their beta-cells have impaired glucose tolerance due to impaired beta-cell function. Dr. Janine Kruit is working to determine the specific role of ABC transporters in beta-cell function, glucose metabolism and type 2 diabetes. Her research will focus on the cholesterol transporters ABCA1 and ABCG1. Her studies could suggest a novel mechanism for how type 2 diabetes develops, and lead to new ways to prevent and treat this disease.
Amphetamine induced changes in prefrontal cortex networks
Studies show that many brain areas are affected by drugs of abuse. The prefrontal cortex (PFC), however, plays an especially pivotal role in how addiction is manifested. Studies of addicted individuals show they have a reduced capacity to perform PFC dependent tasks, such as working memory (a process using multiple memory systems to facilitate problem solving and choose appropriate behaviours). Human studies also show abnormal activity patterns of the PFC in addicted individuals. When tested during withdrawal, the PFC of addicts remains inactive in response to cues that signal the delivery of natural rewards, such as food. In contrast, when they are given a cue that signals the delivery of a drug reward, addicts show both increased activation of their frontal areas and a high level of self-reported drug craving. Taken together, these data suggest an important component of compulsive drug taking. Linking the behavioural changes that an addict goes through to the underlying physiological changes that neural networks undergo is important for understanding the neurobiology of addiction. Dr. Christopher Lapish is studying the behavioral and neurophysiological changes that characterize the addicted state. His experiments will help delineate the neurophysiological changes that occur in the PFC during the process of addiction. By identifying the specific brain patterns that are induced by addiction, he hopes his work will result in a powerful tool to assess specific pharmacological treatments that may abolish them.
Role of Akt phosphorylation of GluR1 subunit of AMPA receptors in the receptor trafficking and synaptic plasticity
Communication between neurons (brain cells) occurs at specialized junctions known as synapses. The process involves presynaptic neurons releasing neurotransmitter molecules, which then bind to membrane receptors on the surface of postsynaptic neurons – triggering the postsynaptic neuron to “fire.” The normal function of the brain depends on balancing the number of active receptors at the synaptic junction, so that neurons fire appropriately. Alzheimer’s disease and mental retardation show decreased receptor activity, whereas epilepsy and stroke show an excess of receptor activation. In effect, these conditions are marked by neural transmissions that are either too weak or too strong. Dr. Jun Liu previously practiced as a neurosurgeon in his native China. Now, he is studying how cellular and molecular mechanisms in brain cells support learning and memory. Recent findings indicate that the number of receptors activated on postsynaptic neurons can be rapidly regulated, suggesting a novel and efficient means by which the strength of synaptic transmission can be altered. Liu is investigating how such rapid changes in the number of postsynaptic receptors, and hence synaptic transmission strength, are initiated and carried out. Improved understanding of how receptor activity is regulated will help researchers learn how to correct receptor imbalances, offering new hope for a number of debilitating neurological conditions.