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Martin Oheim"Astroglial exocytosis: a note of caution from the perspective of a single-vesicle spectrosopist"

Abstract :

Glial cells have recently been implicated in bidirectional signaling from and to neurons at central synapses.
Equiped with a plethora of neurotransmitter receptors and releasing neuroactive substances that classically have been considered as transmitters and neuromodulators of only neuronal origin, astroglia are increasingly being placed in the concept of a 'tripartite synapse' that -in addition to the classically recognized pre- and postsynaptic compartments-- involves glial processes that actively stimulate neuronal activity. Among the different pathways suggested for a regulated 'gliotransmitter' release, our lab has focused on the Ca(2+)-regulated vesicular (exocytotic) release of neuroactive substances by cortical astroglia. Using a combination of molecular genetics, single-vesicle imaging and spectrocopic techniques, we tagged, tracked and classifed astroglial vesicular compartments and their response to various challenges. Our data contradicts earlier observations of a large abundance of glutamatergic near-membrane vesicles in cultured astroglia and calls for a reconsideration of co-localization data based on EGFP expression and Acridine Orange labelling. Instead, we emphasize the importance of a highly dynamic population of secretory lysosomes. 

Selected publications

M. Oheim, F. Kirchhoff, W. Stühmer, 2006. Calcium microdomains in regulated exocytosis. Cell Calcium. press.
F. Nadrigny, I. Rivals, P. Hirrlinger, A. Koulakoff, L. Personnaz, M. Vernet, M. Allioux, M. Chaumeil, N. Ropert, C. Giaume, F. Kirchhoff, M. Oheim, 2006. Detecting fluorescent protein expression and co-localisation on single secretory vesicles with linear spectral unmixing.. European Biophysical Journal. vol.35. 6. august. 533-47.

M. Oheim , DJ. Michael , M. Geisbauer , D. Madsen , RH. Chow, 2006. Principles of two-photon excitation fluorescence microscopy and other nonlinear imaging approaches. Adv. Drug Delivery Rev. vol.doi:10.1016.j.addr.2006.07.005.

Jean Pierre Mothet