Kevin C. Courtney, PhD

Research Interests

Research topic:

Mechanisms of intracellular membrane trafficking and the regulation of membrane fusion in mammalian cells

Research overview:

A defining feature of complex cellular life involves the compartmentalization of specialized molecular components within phospholipid bilayers. These phospholipid bilayers separate one cell from another and also allow for the formation of distinct sub-cellular organelles, such as mitochondria, lysosomes and synaptic vesicles. The mechanisms that underlie the creation and maintenance of these specialized membrane-delimited structures remain controversial. In particular, many sub-cellular organelles undergo SNARE-mediated membrane fusion to merge discrete phospholipid bilayers, followed by sorting and recycling of the components, yet the identities and functions of many of the molecular players that regulate these fusion reactions are unknown. Although the SNARE proteins are considered the core of the membrane fusion machinery, other proteinaceous and lipidic factors are critical for determining when, and if, a fusion reaction can proceed. Moreover, each sub-cellular organelle contains a unique combination of SNAREs that provide specificity and, importantly, each fusion paradigm is also governed by a unique combination of regulatory factors.

The primary goal of the Courtney lab is to both identify and characterize factors that regulate membrane fusion reactions in mammalian cells. Projects involve the examination of protein and lipid factors that govern the fusion reactions that mediate synaptic vesicle exocytosis and lysosome-autophagosome fusion, among others. The lab uses a two-pronged approach using 1) in vitro biochemistry to reconstitute the nano-mechanics of membrane fusion using reduced systems in combination with 2) cell biology, with emphasis on fluorescence microscopy, to test the in vitro principles, and vice versa.

Publications

Courtney KC, Mandal T, Mehta N, Wu L, Li Y, Das D, Cui Q, Chapman ER. (2023) Synaptotagmin-7 outperforms synaptotagmin-1 to promote the formation of large, stable fusion pores via robust membrane penetration. Nature Communications 14, 7761. https://doi.org/10.1038/s41467-023-42497-8

Courtney KC*, Wu L*, Mandal T, Swift M, Zhang Z, Alaghemandi M, Wu Z, Bradberry MM, Deo C, Lavis LD, Volkmann N, Hanein D, Cui Q, Bao H, Chapman ER. (2022) The complexin C-terminal amphipathic helix stabilizes the fusion pore open state by sculpting membranes. Nature Structural & Molecular Biology 29, 97–107. https://doi.org/10.1038/s41594-021-00716-0.

Courtney KC*, Vevea JD*, Li Y*, Wu Z, Zhang Z, Chapman ER. (2021) Synaptotagmin 1 oligomerization via the juxtamembrane linker regulates spontaneous and evoked neurotransmitter release. Proceedings of the National Academy of Sciences 118 (48) e2113859118; https://doi.org/10.1073/pnas.2113859118.

Vevea JD, Kusick GF, Courtney KC, Chen E, Watanabe S, Chapman ER. (2021) Synaptotagmin 7 is enriched at the plasma membrane to promote vesicle docking and control synaptic plasticity. eLife 2021;10:e67261 DOI: 10.7554/eLife.67261

Wu L, Courtney KC, Chapman ER. (2021) Cholesterol stabilizes recombinant exocytic fusion pores by altering membrane bending rigidity. Biophysical Journal, 120(8). DOI: 10.1016/j.bpj.2021.02.005.

Liu L*, Courtney KC*, Huth SW, Rank LA, Weisblum B, Chapman ER, Gellman SH. (2021) Beyond Amphiphilic Balance: Changing Subunit Stereochemistry Alters the PoreForming Activity of Nylon-3 Polymers. Journal of the American Chemical Society, 143(8). DOI: 10.1021/jacs.0c12731.

Das D, Bao H, Courtney KC, Wu L, Chapman ER. (2020) Resolving kinetic intermediates during the regulated assembly and disassembly of fusion pores. Nature Communications, 11(231). DOI: 10.1038/s41467-019-14072-7.

Courtney KC, Shahidi S, Maxfield FR, Fairn GD, Zha X. (2018) Comment on "Orthogonal lipid sensors identify transbilayer asymmetry of plasma membrane cholesterol. eLife, 7, 8, DOI: 10.7554/eLife.38493.

Courtney KC, Pezeshkian W, Raghupathy R, Zhang C, Ipsen, JH, Ford DA, Khandelia H, Presley JF, Zha X. (2018) C24 sphingolipids govern the transbilayer asymmetry of cholesterol and lateral organization of model and live cell plasma membranes. Cell Reports, 24(4), 1037-1049. DOI: 10.1016/j.celrep.2018.06.104.

Eid W, Dauner K, Courtney KC, Gagnon A, Parks RJ, Sorisky A, Zha X (2017) mTORC1 Activates SREBP-2 by Suppressing Cholesterol Trafficking to the Lysosomes in Mammalian Cells. Proceedings of the National Academy of Sciences, 114(30), 7999- 8004. DOI: 10.1073/pnas.1705304114.

Dong F, Mo Z, Eid W, Courtney KC, Zha X (2014) Akt Inhibition Promotes ABCA1- Mediated Cholesterol Efflux to ApoA-I through Suppressing mTORC1. PLOS ONE 9(11): e113789. DOI: 10.1371/journal.pone.0113789.

Courtney KC, Bainard LD, Sikes BA, Koch AM, Maherali H, Klironomos JN, Hart MM (2012) Determining a Minimum Detection Threshold in Terminal Restriction Fragment Length Polymorphism Analysis. Journal of Microbiological Methods, 88(1), 14-18.