Heidi M. McBride
Ph.D., (Biochemistry, McGill)
Associate Professor, Department of Pathology and Laboratory Medicine, Faculty of Medicine,
Researcher, University of Ottawa Heart Institute
Telephone: (613) 761-4701
Fax: (613) 761-5281
Other website: http://www.ottawaheart.ca/UOHI/bio/Heidi_McBride.jsp
Areas of Interest and Expertise
The GTPase molecular switches are proteins with an "on" or "off" state that govern the cellular responses to most environmental challenges. The function of each GTPase is finely balanced through the combinatorial use of intersecting switches that unify the response of the cell, tissue and organism. For example, in the field of intracellular transport, we are beginning to understand the molecular communication between GTPases governing the formation of budded vesicles (Arf proteins) and the GTPases that determine the final destination of that vesicle (Rab proteins). In addition, recent work has uncovered exciting molecular links between Ras regulated signal transduction pathways, and the activation of the Rab 5 GTPase, which regulates endocytic transport. This helps us to understand how endocytic events are coupled to receptor-ligand interactions at the cell surface. Although there has been a concentrated effort over the past 15 years to identify the machinery that governs the secretory and endocytic pathways, the participation of the mitochondrion within the intracellular community has attracted the attention of researchers only in the last few years. There are at least two important GTPases that function in the regulation of mitochondrial morphology, and the challenge now is to identify the molecular mechanisms driving their action. Mitochondria fuse regularly with each other, and this is balanced by the action of fission and motility events along microtubules. The hypothesis driving Dr. McBride's work is that GTPase molecular switches govern the dynamics, morpholology, and ultimately the metabolic output, of the mitochondria. Her objectives are to systematically evaluate the three elements contributing to mitochondrial morphology in mammalian cells (fusion, fission and motility), with a specific focus on the regulatory switches that govern them. Importantly, by investigating essential aspects of mitochondrial morphology, she hopes to uncover new molecular links that integrate the functional output of the mitochondria with signaling events that result in normal (and abnormal) cellular behavior.
Mitochondria are dynamic and fuse regularly. The image is a cropped movie showing only a few mitochondria under steady state within a COS7 cell that has been transiently transfected with the matrix targeted pOCT-YFP (so we can visualize the mitochondria). Shown here are 100 images taken every 2 seconds. What we see is that the smaller mitochondria clearly becomes fused with the larger one, and the first important question is: why do mitochondria fuse? What is the information that they are carrying to one another? It is surprising, but we have no real answer to this question. The second major question is: How do they fuse? Mitochondria have two membrane bilayers, and in order for complete fusion, both membranes must fuse, so what is the molecular mechanism that mediates this extremely complex event? We have also seen many examples of mitochondria dividing and transiently interacting with one another in all the cells we have examined. These events occur at steady state, without any obvious requirement for cell division, or external stimulation. By examining the molecular machinery that governs mitochondrial dynamics, we hope to understand more about how the mitochondria is integrated within the cellular community as a whole.
- Neuspiel, M., Schauss, A.C., Braschi, E., Zunino, R., Rippstein, P., Rachubinski, R.A., Andrade-Navarro, M.A., and McBride, H.M. Cargo-selected transport from the mitochondria to peroxisomes is mediated by vesicular carriers. Current Biology. 18(2), 102-108, 2008.
- Wasiak, S., Zunino, R. and McBride, H.M. Bax/Bak promote SUMOylation of DRP1 and its stable association with mitochondria during apoptotic cell death. Journal of Cell Biology. 177: 439-450, 2007
- Zunino, R., Rippstein, P., Andrade-Navarro, M., and McBride, H.M. The SUMO protease SenP5 is required to maintain mitochondrial morphology and function. Journal of Cell Science, 120(7):1178-1188, 2007
- Schauss, A,C. and McBride, H.M. Mitochondrial Fission: A Non-Nuclear Role for Num1p Current Biology Vol 17, R467-R470, 2007 (Dispatch).
- Jahani-Asl, A., Cheung, E.C.C., Neuspiel, M., Xu, W., MacLaurin, J.G., Fortin, A., Park, D.S., McBride, H.M.*, Slack, R.S. Dynamic fusion of mitochondria protects neurons against oxidative stress and exitotoxicity. J. Biol Chem. 282(33):23788-98, 2007. * co-corresponding author.
- McBride, H.M., Neuspiel, M., Wasiak, S. Mitochondria: More than just a powerhouse. Current Biology. Review. 16(14):R551-R560, 2006.
- Jeyaraju, D., Xu, L., Letellier, M.C, Davidovic, L., Berg, E.A., McBride, H.M*, and Pellegrini, L. Phosphorylation of the vertibrate rhomboid protease PARL regulates mitochondrial morphology. PNAS (Track II),103(49) 18562-18567, 2006 * co-corresponding author. (Jayaraju and Xu co-first author)
- Neuspiel, M., Zunino, R., Gangaraju, S., Rippstein, P. and McBride H.M. Activated Mfn2 has signaling capabilities, represses Bax activation and protects against permeability transition. J. Biol. Chem. 280(26):25060-25070, 2005.
- Germain, M., Mathai, J.P., McBride, H.M*, and Shore, G.C. Endoplasmic reticulum BIK initiates DRP1-regulated remodelling of mitochondrial cristae and mobilization of cytochrome c during apoptosis. EMBO J. 24(8):1546-56, 2005 * co-corresponding author.
- Harder, Z., Zunino, R., and McBride, H. SUMO-1 participates with DRP1 in mitochondrial fission events. Current Biology, 14: 340-345, 2004.