The Journal of Neuroscience, 2000, 20:RC67:1-5
RAPID COMMUNICATION
Developmental Changes in the Subcellular Localization of
Calretinin
Nicola J.
Hack,
Mark C.
Wride,
Kathleen M.
Charters,
Stanley B.
Kater, and
Thomas N.
Parks
Department of Neurobiology and Anatomy, University of Utah School
of Medicine, Salt Lake City, Utah 84132
Brainstem auditory neurons in the chick nucleus magnocellularis
(NM) express high levels of the neuron-specific calcium-binding protein
calretinin (CR). CR has heretofore been considered a diffusible calcium
buffer that is dispersed uniformly throughout the cytosol. Using
high-resolution confocal microscopy and complementary biochemical analyses, we have found that during the development of NM neurons, CR
changes from being expressed diffusely at low concentrations to being
highly concentrated beneath the plasma membrane. This shift in CR
localization occurs at the same time as the onset of spontaneous
activity, synaptic transmission, and synapse refinement in NM. In the
chick brainstem auditory pathway, this subcellular localization appears
to occur only in NM neurons and only with respect to CR, because
calmodulin remains diffusely expressed in NM. Biochemical analyses show
the association of calretinin with the membrane is detergent-soluble
and calcium-independent. Because these are highly active neurons with a
large number of Ca2+-permeable synaptic AMPA
receptors, we hypothesize that localization of CR beneath the plasma
membrane is an adaptation to spatially restrict the calcium influxes.
Key words:
calcium-binding proteins; auditory neurons; calcium
homeostasis; calretinin; subcellular localization; nucleus
magnocellularis
Copyright © 2000 Society for Neuroscience 0270-6474/00/$05.00/0