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- Title
Endogenous Ca<sup>2+</sup> Buffer Concentration and Ca<sup>2+</sup> Microdomains in Hippocampal Neurons.
- Authors
Müller, Andreas; Kukley, Maria; Stausberg, Pia; Beck, Heinz; Müller, Wolfgang; Dietrich, Dirk
- Abstract
Ca2+-binding proteins are ubiquitously expressed throughout the CNS and serve as valuable immunohistochemical markers for certain types of neurons. However, the functional role of most Ca2+ -binding proteins has to date remained obscure because their concentration in central neurons is not known. In this study, we investigate the intracellular concentration of the widely expressed Ca2+-binding protein calbindin-D28k in adult hippocampal slices using patch-clamp recordings and immunohistochemistry. First, we show that calbindin-D28k freely exchanges between patch pipette and cytoplasm during whole cell patch-clamp recordings with a time constant of ∼10 min. Substituting known concentrations of recombinant calbindin-D28k in patch pipettes enabled us to determine the endogenous calbindin-D28k concentration by postrecording immunohistochemistry. Using this calibration procedure, we find that mature granule cells (doublecortin--) contain ∼40 µM, and newborn granule cells (doublecortin+) contain 0-20 µM calbindin-D28k. CA3 stratum radiatum interneurons and CA1 pyramidal cells enclose ∼47 and ∼45 µM calbindin-D28k, respectively. Numerical simulations showed that 40 µM calbindin-D28k is capable of tuning Ca2+ microdomains associated with action potentials at the mouth of single or clustered Ca2+ channels: calbindin-D28k reduces the increment in free Ca2+ at a distance of 100 and 200 nm by 20 and 35%, respectively, and strongly accelerates the collapse of the Ca2+ gradient after cessation of Ca2+ influx. These data suggest that calbindin-D28k equips hippocampal neurons with ∼160 µM mobile, high-affinity Ca2+-binding sites (κS ∼ 200) that slow and reduce global Ca2+ signals while they enhance the...
- Subjects
CARRIER proteins; CALCIUM-binding proteins; CALCIUM; NEURONS; CONFOCAL microscopy; DEVELOPMENTAL neurobiology
- Publication
Journal of Neuroscience, 2005, Vol 25, Issue 3, p558
- ISSN
0270-6474
- Publication type
Article
- DOI
10.1523/JNEUROSCI.3799-04.2005