Harvey McMahon

Molecular mechanism of Parkinson’s disease
Group Leader page

Project 1: Parkinson’s disease: the importance of mitochondria to maintenance of synaptic function

Synaptic dysfunction has long been known to play a role in the onset of Parkinson’s. Drugs that affect neuronal synaptic function can induce Parkinsonian symptoms while mutations of the mitochondrial PINK and PARKIN proteins are found in patients with the disease.

This project aims to find out what happens to synapses when mitochondrial stop functioning optimally.  We have found in fibroblast models, that a number of risk factor proteins for Parkinson’s affect mitochondrial function. We would now like to move this work from fibroblasts into neurons where mitochondria are enriched in synapses and are necessary for synaptic function. Here we will study endocytosis and exocytosis in cultured neurons while manipulation risk factors for the disease.

Understanding how mitochondria contribute to synaptic function and equally how dysfunction contributes to neuronal loss may be key to understanding the progression the disease.  In addition, we hope this work will contribute useful mechanisms to be able to protect against energy deficits and thus increase neuronal health to protect against disease progression.

We will try to understand the normal function of risk factors for the disease. In addition we will be looking for new drug targets to protect against mitochondrial dysfunction.

References:

Simcox, E. M., Reeve, A., & Turnbull, D. (2013).
Monitoring mitochondrial dynamics and complex I dysfunction in neurons: implications for Parkinson's disease.
Biochemical Society Transactions, 41(6), 1618–1624.

Boucrot, E., et. al. (2015).
Endophilin marks and controls a clathrin-independent endocytic pathway.
Nature, 517(7535), 460–465.

Boucrot, E., et. al. (2012).
Membrane fission is promoted by insertion of amphipathic helices and is restricted by crescent BAR domains.
Cell, 149(1), 124–136.

Llobet, A., Gallop, J. L., Burden, J. J. E., Camdere, G., Chandra, P., Vallis, Y., et al. (2011).
Endophilin drives the fast mode of vesicle retrieval in a ribbon synapse.
The Journal of Neuroscience : the Official Journal of the Society for Neuroscience, 31(23), 8512–8519.

Peter, B. J., et. al. (2004).
BAR domains as sensors of membrane curvature: the amphiphysin BAR structure.
Science (New York, N.Y.), 303(5657), 495–499.


Project 2: Analysis of brain synapse activity and the role of endophilin in its maintenance

Endophilin-1 is brain specific and highly concentrated in synapses where it is proposed to be involved in clathrin-mediated endocytosis. We however have recently shown in fibroblast that endophilin-2 marks a non-clathrin dependent pathway of endocytosis, where it is responsible for the internalization of many G-protein coupled receptors and growth-factor receptors.  By extension one might propose that the neuronal homologue will have a similar function in synaptic vesicle retrieval.

We culture hippocampal neurons, and have a microscopy setup along with appropriate software to measure and analyse exocytosis of synaptic vesicles in response to electrical depolarization, and their subsequent endocytosis. We also have viral knockdown of protein in place and would now like to analyse the role of proteins like endophilin and other BAR-domain containing proteins (that are enriched in nerve terminals) in vesicle dynamics.

This project will help us understand how the brain works to maintain synaptic function under conditions of light versus intense activity and following various drug treatments, and in animal models of neurodegeneration and synaptic dysfunction. Proteins that cause specific disruption of activity will be further analysed in non-neuronal cell culture models and in vitro, for binding partners and for their mechanisms of action.


References:

Boucrot, E., et. al. (2015).
Endophilin marks and controls a clathrin-independent endocytic pathway.
Nature, 517(7535), 460–465.

Renard, H.-F., Simunovic, M., Lemière, J., Boucrot, E., Garcia-Castillo, M. D., Arumugam, S., et al. (2015).
Endophilin-A2 functions in membrane scission in clathrin-independent endocytosis.
Nature, 517(7535), 493–496.

Boucrot, E., et. al. (2012).
Membrane fission is promoted by insertion of amphipathic helices and is restricted by crescent BAR domains.
Cell, 149(1), 124–136.

Llobet, A., Gallop, J. L., Burden, J. J. E., Camdere, G., Chandra, P., Vallis, Y., et al. (2011).
Endophilin drives the fast mode of vesicle retrieval in a ribbon synapse.
The Journal of Neuroscience : the Official Journal of the Society for Neuroscience, 31(23), 8512–8519.

McMahon, H. T. and Boucrot, E. (2011).
Molecular mechanism and physiological functions of clathrin-mediated endocytosis.
Nature Reviews. Molecular Cell Biology, 12(8), 517–533.

Jao, C. C., Hegde, B. G., Gallop, J. L., Hegde, P. B., McMahon, H. T., Haworth, I. S. and Langen, R. (2010).
Roles of amphipathic helices and the bin/amphiphysin/rvs (BAR) domain of endophilin in membrane curvature generation.
The Journal of Biological Chemistry, 285(26), 20164–20170.

Gallop, J. L., Butler, P. J. G. and McMahon, H. T. (2005).
Endophilin and CtBP/BARS are not acyl transferases in endocytosis or Golgi fission.
Nature, 438(7068), 675–678.

Peter, B. J., et. al. (2004).
BAR domains as sensors of membrane curvature: the amphiphysin BAR structure.
Science (New York, N.Y.), 303(5657), 495–499.


All these papers can be found on our website: endocytosis.org