Cell biological mechanisms underlying neuronal excitability and synaptic plasticity

Dr Josef Kittler
MRC Senior Non-Clinical Fellow
Tel: +44 (0)20 7679 3218
Email: j.kittler@ucl.ac.uk

Lab Members:

  • Sana Al Awabdh
  • Nicol Birsa
  • Elizabeth Davenport
  • Ramona Eckel (joint with Matthew Walker, IoN)
  • Nathalie Higgs
  • Davor Ivankovic
  • Guillermo Lopez-Domenech
  • Souvik Modi
  • James Muir
  • Rosalind Norkett
  • Manav Pathania
  • David Sheehan (joint with Lewis Griffin, Computer Science)
  • Terri Stephen (joint with Tom Mrsic-Flogel, NPP)
  • Victoria Vaccaro


JK1

Dr Josef Kittler graduated in 1996 with a degree in Biochemistry from the University of Bath. He carried out PhD and postdoctoral studies with Stephen Moss at the MRC Laboratory for Molecular Cell Biology, UCL. Following a Wellcome Trust Advanced Training Fellowship with David Attwell in the Department of Physiology at UCL he was awarded in 2005 an MRC Career Development Award to establish his independent research group. He is currently an editor of the Journal of Biological Chemistry.


Overview Nerve cells in the brain have a highly spatially diverse cellular and subcellular architecture including axon, cell body, and dendrites as major cellular compartments, in addition to subcellular membrane microdomains such as spines, synapses and the secretory and endosomal networks. To ensure efficient signaling between neurons, and to ensure that the correct levels of neuronal activity are maintained, it is critical that mechanisms exist to tightly regulate the selective transport and localisation of ion channels, receptors and organelles to these specific neuronal subdomains. We are interested in understanding the contribution played by intracellular transport and membrane trafficking of proteins and organelles in regulating the activity and plasticity of synapses.

We focus on three major research themes: Firstly, we are studying the molecular and cellular mechanisms regulating the function and membrane trafficking of neurotransmitter receptors and transporters and the role this plays in controlling synaptic transmission and hence the levels of neuronal excitability in the brain. We are similarly interested in how the function of synapses can be controlled by the regulated trafficking of organelles such as mitochondria. Secondly, we concentrate on how intracellular transport is regulated by post-translational modifications such as phosphorylation, palmitoylation and ubiquitination. Thirdly, we wish to understand better how the trafficking of receptors, transporters and other cargo may be altered in neurological and neuropsychiatric diseases. We combine the use of various techniques, including molecular and cell biology, protein biochemistry, patch clamp electrophysiology, neuronal transfection, and fixed and live cell confocal and CCD imaging. We also use fluorescent protein and Quantum Dot labeling approaches to study the membrane dynamics of proteins of interest.

GABAA receptor trafficking and the molecular mechanisms that regulate the plasticity of inhibitory synapses

JKimage1
Synaptic GABAA receptor clusters imaged by immunofluorescence and confocal microscopy Structure of a GABAAR endocytosis motif complexed with the clathrin adaptor AP2 (from Kittler et al., 2008)


GABAA receptors are ligand-gated ion channels that mediate the majority of fast inhibitory neurotransmission in the central nervous system. We are interested in the mechanisms that regulate the number of GABAA receptors at inhibitory synapses to control the strength and plasticity of these synapses. In particular we focus on identifying and characterising protein complexes important for regulating receptor anchoring at synapses and receptor transport through the secretory and endocytic compartments. We also study the cross-talk between post-translational modification of the GABAA receptor (by phosphorylation, ubiquitination and palmitoylation) and receptor membrane trafficking and in particular how phosphorylation can act as regulatory switch for the regulated membrane trafficking of receptors towards and away from synapses.

JKimage2 GABAA receptor membrane dynamics imaged in live neurons using semi-conductor nanocrystals (Quantum Dots)


Glutamate transporter trafficking

Maintaining the correct levels of extracellular glutamate is crucial for the control of cell and network activity in the brain and for nerve cell survival. Glutamate uptake is controlled by glutamate transporters present on both neurons and glia, which play a critical role in shaping synaptic transmission and in keeping extracellular glutamate below excitotoxic levels. the dysfunction of these transporters is implicated in several neurological diseases including epilepsy, stroke and motor neuron disease. Understanding how neurons and glial cells regulate glutamate transporter function has important implications for understanding of how neuronal activity is controlled and how disrupted glutamate uptake may contribute to pathology. We are interested in understanding better the role of glutamate transporter associated proteins (or modifying enzymes) in regulating transporter activity and trafficking under normal and pathological conditions.

JKimage3 Live cell imaging of the membrane trafficking of GFP-glutamate transporter containing vesicles in transfected cells


Organellar trafficking in neurons

We are interested in the mechanisms that underlie the activity dependent transport and localisation or organelles within neurons under normal conditions and during excitotoxicity. In particular we focus on the mechanisms that regulate the transport and morphology of mitochondria and endocytic compartments within dendrites and the role of motor proteins and adaptors in this process. We are also investigating how proteins implicated in pathology, such as the schizophrenia protein disc1, are involved in intracellular transport in neurons.

JKimage4

Live cell confocal imaging of mitochondrial transport dynamics in a hippocampal neuron


For additional information on our research interests and a full publication list with links to pubmed please also visit our UCL Neuroscience profile:

http://www.ucl.ac.uk/npp/people/kittler-josef

Selected publications:

  • Twelvetrees AE, Yuen EY, Arancibia-Carcamo IL, MacAskill AF, Rostaing P, Lumb MJ, Humbert S, Triller A, Saudou F, Yan Z, Kittler JT (2010). Delivery of GABAARs to synapses is mediated by HAP1-KIF5 and disrupted by mutant huntingtin. Neuron 65, 53-65.
  • Macaskill AF, Kittler JT (2010). Control of mitochondrial transport and localization in neurons. Trends Cell Biol.
  • Arancibia-Carcamo I.L., Kittler,J.T. (2009). Regulation of GABAA receptor membrane trafficking and synaptic localization. Pharmacology and Therapeutics 123, 17-31.
  • Arancibia-Carcamo IL, Yuen EY, Muir J, Lumb MJ, Michels G, Saliba RS, Smart TG, Yan Z, Kittler JT* and Moss SJ* (*co-senior author) (2009). Ubiquitin-dependent lysosomal targeting of GABAA receptors regulates neuronal inhibition. PNAS 106, 17552-17557.
  • MacAskill AF, Rinholm JE, Twelvetrees AE, Arancibia-Carcamo IL, Muir J, Fransson A, Aspenstrom P, Attwell D and Kittler JT (2009). Miro1 is a calcium sensor for glutamate receptor-dependent localization of mitochondria at synapses. Neuron 61, 541-555. (see also the preview by Cai and Sheng in the same issue of Neuron).
  • Kittler JT, Chen G, Kukhtina V, Vahedi-Faridi A, Tretter V, Smith KR, McAinsh K, Arancibia-Carcamo L, Saenger W, Haucke V, Yan Z and Moss SJ (2008) Regulation of synaptic inhibition by phospho-depedent binding of the AP2 complex to a YECL motif in the GABAA receptor g2 subunit PNAS. 105:3616-21.
  • Kittler JT (2006) Censoring the editor in transient forebrain ischemia. Neuron. 2;49:646-8.

Books

  • JKimage5

    The Dynamic Synapse Kittler JT and Moss SJ Eds (2006)

  • The Dynamic Synapse: Molecular Methods In Ionotropic Receptor Biology Frontiers in Neuroscience, CRC Press