Atherosclerosis Laboratory Projects
 

1. Control of cholesterol export from macrophages.

We are studying the roles of the cholesterol transporters ABCA1 and ABCG1 in the export of excess cholesterol from macrophages. A related interest is in defining which species of HDL interact with these transporters to accept and remove cellular cholesterol, and how HDL quality may be compromised in some disease states, such as cardiovascular disease and diabetes. The overall aim of these studies is to understand how cholesterol accumulation in the vascular wall may be prevented or reversed, to reduce the incidence and impact of atherosclerosis.

Prof Wendy Jessup
Prof Leonard Kritharides

References:
Hsieh V, Kim MJ, Gelissen IC, Brown AJ, Sandoval C, Hallab JC, Kockx M, Traini M, Jessup W, Kritharides L. Cellular cholesterol regulates ubiquitination and degradation of the cholesterol export proteins ABCA1 and ABCG1. J Biol Chem 2014 Feb 5
Gelissen IC, Harris M, Rye KA, Quinn C, Brown AJ, Kockx M, Cartland S, Packianathan M, Kritharides L, Jessup W. ABCA1 and ABCG1 synergize to mediate cholesterol export to apoA-I. Arterioscler Thromb Vasc Biol 2006;26:534-540

2. Cardiovascular side effects of cyclosporin A

Cyclosporin A (CsA) is an immunosuppressant drug that is commonly used in organ transplant recipients. Unfortunately, treatment with CsA has been associated with elevated plasma levels of cholesterol and triglycerides and increased risk of atherosclerosis. Studies in our lab are investigating the pathways by which CsA increases plasma cholesterol and triglyceride levels as well as how CsA affects the formation of atherosclerotic lesions using mouse models.

Dr Maaike Kockx

References:
Kockx M, Jessup W, Kritharides L. Cyclosporin A and atherosclerosis – Cellular pathways in atherogenesis. Pharmacol Ther. 2010; 128(1): 106-18
Kockx M, Guo DL, Traini M, Gaus K, Kay J, Rentero C, Wimmer-Kleikamp, S, Burnett JR, Le Goff W, Van Eck M, Stow JL, Jessup W, Kritharides L. Cyclosporin A decreases aplipoprotein E secretion from human macrophages via a protein phosphatase 2B-dependent and ABCA-1 independent pathway. J Biol Chem 2009; 284:24144-54

3. Regulation of constitutive protein secretion from human macrophages

Our group has identified various signalling and trafficking pathways that regulate the constitutive secretion of anti-atherogenic apolipoprotein E (apoE) from human macrophages. We have recently identified several other constitutive secreted proteins which may be transported along with apoE. We are currently investigating pathways that regulate the secretion of these proteins and how they relate to the secretion of apoE.

Dr Maaike Kockx
Prof Leonard Kritharides

References:
Kockx M, Jessup W, Kritharides L. Regulation of endogenous apolipoprotein E secretion by macrophages Arterioscler Thromb Vascular Biol 2008; 28:1060-1067
Kockx M, Guo DL, Huby T, Lesnik P, Kay J, Sabaretnam T, Jary E, Hill M, Gaus K, Chapman J, Stow JL, Jessup W, Kritharides L. Secretion of apolipoprotein E from macrophages occurs via a protein kinase A and calcium-dependent pathway along the microtubule network. Circ Res 2007, 101:607-616
Karunakaran D, Kockx M, Owen DM, Burnett JR, Jessup W, Kritharides L Protein kinase C controls vesicular transport and secretion of apolipoprotein E from primary human macrophages. J. Biol. Chem. 2013 15;288(7):5186-97

4. Glycosylation of apolipoprotein E

Apolipoprotein E (apoE) is an important multi-functional protein, involved in lipid transport and metabolism, regulation of inflammation, and is implicated in the pathogenesis of atherosclerosis and Alzheimer’s Disease. ApoE is secreted from a number of tissues in the body. During its transport through the secretory pathway in the cell, apoE is modified at specific sites with sugars (glycosylation). Attachment of these sugars to apoE is known to be altered in neurodegeneration, preeclampsia, alcoholism and excess cholesterol accumulation. However, the relationship between changes in apoE glycosylation and disease remains unknown.

Our laboratory has used advanced mass spectrometry techniques to identify a new site of glycosylation in human apoE, and has created novel expression systems to produce normally and non-glycosylated human apoE protein. Using these tools together with in vitro and animal models, our aim is to understand how changes in the sites and structure of apoE glycosylation influence the many functions of this protein in health and disease.

Dr Mathew Traini
Dr Maaike Kockx
Prof Leonard Kritharides

References:
LeeY, Kockx M, Raftery MJ, Jessup W, Griffith R, Kritharides L. Glycosylation and sialylation of macrophage-derived apolipoprotein E analysed by SDS-PAGE and mass spectometry – evidence for a novel site of glycosylation on Ser290. Mol Cell Proteomics. 2010; 9(9):1986-81

5. Role of SMPDL3A in inflammatory disease

Atherosclerosis is a disease characterized by the growth of fibrous, calcified, lipid-rich plaques in the walls of blood vessels. During the development of these plaques, immune cells infiltrate the vessel wall, differentiate into macrophages, and accumulate vast quantities of excess cholesterol. These cholesterol-loaded macrophages (also known as “foam cells”) secrete pro-inflammatory signals that attract further immune cells to the plaque, creating a dangerous feedback loop. The journey of macrophage to foam cell is underpinned by complex changes in their gene expression. Understanding these changes, together with their downstream effects, is critical for the development of future therapies to reverse development of the atherosclerotic plaque.

Using gene expression microarrays, our laboratory has identified several new genes that are up-regulated in response to cholesterol loading of human macrophages. One of the most highly up-regulated genes encodes a virtually uncharacterized member of the phosphodiesterase family of enzymes, which is secreted from macrophages. We have discovered this novel enzyme has the unexpected ability to degrade a molecules acting in key inflammatory signaling pathways, making it a potentially important regulator of the immune system. Our current research focus is the development of biochemical, cellular and animal models to better understand how this new enzyme links cholesterol metabolism to immune dysfunction in atherosclerosis and other inflammatory diseases.

Dr Mathew Traini
Prof Wendy Jessup