Transient calbindin-D28k-positive systems in the telencephalon: ganglionic eminence, developing striatum and cerebral cortex.
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Calbindin-D28k (calbindin) is a member of the superfamily of calcium-binding proteins implicated in the regulation of intracellular calcium. In the mature brain, calbindin is widely expressed in neurons of the forebrain and the hindbrain, and in the telencephalon calbindin-like immunoreactivity is particularly strongly expressed by medium-sized neurons of the striatum and by certain other neurons in the cortex and subcortex. We have traced the development of calbindin expression in the forebrain of the rat, and report here that in addition to the steady development of these calbindin-positive neuronal systems, transient waves of calbindin expression occur in cells of the ventricular zones of the basal ganglia and cortex and in cells of the telencephalic regions derived from these ventricular zones including radial glia of the developing striatum. In the striatum and its ventricular zone (the ganglionic eminence, or GE) we identified four transient calbindin-positive systems in the perinatal period. First, calbindin-immunoreactive cells began to appear in the GE by embryonic day (E)18, and by E20 an extensive dorsal and lateral part of the GE was marked by dense calbindin-like immunoreactivity in the ventricular zone. This calbindin system peaked at postnatal day (P)0-P3 and disappeared by P15. Its presence suggests that the GE is divisible on a molecular basis into lateral and medial districts that may correspond to derivatives of the lateral and medial ventricular ridges. Second, a system of calbindin-positive processes appeared in the dorsal and lateral caudoputamen with temporal and spatial distributions matching the germinal zone system. Many of these processes could be traced from calbindin-positive cells in the ventricular zone of the GE, including processes stretching across the full width of the dorsal caudoputamen. Double-staining experiments demonstrated that these radial processes were Rat.401-positive, suggesting that they form a subset of radial glia in the developing telencephalon. These findings demonstrate that during development calbindin is expressed in glial as well as neural cells. They further suggest that the radial glia associated with the GE form heterogeneous populations, the transient calbindin-positive radial glia being associated with the lateral ridge of the GE and its derivatives. Third, a scattered population of calbindin-positive cells with morphologies different from the common medium-sized calbindin-immunoreactive neurons of the striatum appeared in the dorsal and lateral striatum from about E20 to P15. Some of these cells were close to the transient calbindin-positive radial processes in the same region, but others were not.(ABSTRACT TRUNCATED AT 400 WORDS) (+info)
Role of tissue transglutaminase type 2 in calbindin-D28k interaction with ataxin-1.
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Spinocerebellar ataxia-1 (SCA1) is caused by the expansion of a polyglutamine repeats within the disease protein, ataxin-1. The mutant ataxin-1 precipitates as large intranuclear aggregates in the affected neurons. These aggregates may protect neurons from mutant protein and/or trigger neuronal degeneration by encouraging recruitment of other essential proteins. Our previous studies have shown that calcium binding protein calbindin-D28k (CaB) associated with SCAl pathogenesis is recruited to ataxin-l aggregates in Purkinje cells of SCAl mice. Since our recent findings suggest that tissue transglutaminase 2 (TG2) may be involved in crosslinking and aggregation of ataxin-l, the present study was initiated to determine if TG2 has any role in CaB-ataxin-l interaction. The guinea pig TG2 covalently crosslinked purified rat brain CaB. Time dependent progressive increase in aggregation produced large multimers, which stayed on top of the gel. CaB interaction with ataxin-l was studied using HeLa cell lysates expressing GFP and GFP tagged ataxin-l with normal and expanded polyglutamine repeats (Q2, Q30 and Q82). The reaction products were analyzed by Western blots using anti-polyglutamine, CaB or GFP antibodies. CaB interacted with ataxin-1 independent of TG2 as the protein-protein crosslinker DSS stabilized CaB-ataxin-l complex. TG2 crosslinked CaB preferentially with Q82 ataxin-1. The crosslinking was inhibited with EGTA or TG2 inhibitor cystamine. The present data indicate that CaB may be a TG2 substrate. In addition, aggregates of mutant ataxin-l may recruit CaB via TG2 mediated covalent crosslinking, further supporting the argument that ataxin-l aggregates may be toxic to neurons. (+info)
Effects of furosemide on renal calcium handling.
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Furosemide is a loop diuretic agent that has been used to treat hypercalcemia because it increases renal calcium excretion. The effect of furosemide on calcium transport molecules in distal tubules has yet to be investigated. We conducted studies to examine the effects of furosemide on renal calcium excretion and expression of calcium transport molecules in mice. Mice were administered with a single dose of furosemide (15 mg/kg) and examined 4 h later or were given twice-daily furosemide injections for 3 days. To evaluate the effects of volume depletion, drinking water was supplemented with salt. Our results showed that, in acute experiments, furosemide enhanced urinary calcium excretion, which was associated with a significant increase in mRNA levels of TRPV5, TRPV6, and calbindin-D28k but not calbindin-D9k as measured by real-time PCR (TRPV5 and TRPV6 are transient receptor potential vanilloid 5 and 6). Chronic furosemide administration induced three- to fourfold increases in urinary calcium excretion and elevated mRNA levels of TRPV5, TRPV6, calbindin-D28k, and calbindin-D9k without or with salt supplement. Similar upregulation of calcium transport molecules was observed in mice with gentamicin-induced hypercalciuria. Coadministration of chlorothiazide decreased furosemide-induced calciuria, either acutely or chronically, although still accompanied by upregulation of these transport molecules. Immunofluorescent staining studies revealed comparably increased protein abundance in TRPV5 and calbindin-D28k. We conclude that furosemide treatment enhances urinary calcium excretion. Increased abundance of calcium transport molecules in the distal convoluted tubule represents a solute load-dependent effect in response to increased calcium delivery and serves as a compensatory adaptation in the downstream segment. (+info)
Calbindin-D9k and parvalbumin are exclusively located along basolateral membranes in rat distal nephron.
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There is strong evidence that vitamin D-dependent Ca(2+)-binding proteins, i.e., calbindin-D9k and calbindin-D28k, facilitate diffusion of Ca2+ through the cytosolic compartment of renal and intestinal cells, which transport Ca2+ transcellularly. In the study presented here, parvalbumin, calbindin-D9k, and calbindin-D28k were localized precisely by immunocytochemistry in rat kidney. Antisera recognizing specifically the thick ascending loop of Henle, the connecting tubules and collecting ducts, and the intercalated cells of the collecting ducts were used to identify different cell types. In rat kidney cortex, parvalbumin and calbindin-D9k colocalized in the thick ascending loop of Henle, the distal convoluted tubule, the connecting tubule, and the intercalated cells of the collecting duct. Strikingly, in all responsive cells, parvalbumin and calbindin-D9k were exclusively present in a thin layer along the basolateral membrane. In contrast, calbindin-D28k was only present in the distal convoluted and connecting tubule, where it was evenly distributed through the cytosol. In conclusion, the exclusive localization of parvalbumin and calbindin-D9k at the basolateral membrane of immunopositive renal cells implies their involvement in the regulation of transport processes located in these membranes rather than a role as intracellular Ca2+ buffer and Ca2+ shuttle between the two opposing membranes. (+info)
Peptide binding proclivities of calcium loaded calbindin-D28k.
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Calbindin-D28k is known to function as a calcium-buffering protein in the cell. Moreover, recent evidence shows that it also plays a role as a sensor. Using circular dichroism and NMR, we show that calbindin-D28k undergoes significant conformational changes upon binding calcium, whereas only minor changes occur when binding target peptides in its Ca(2+)-loaded state. NMR experiments also identify residues that undergo chemical shift changes as a result of peptide binding. The subsequent use of computational protein-protein docking protocols produce a model describing the interaction interface between calbindin-D28k and its target peptides. (+info)
Crystallization and preliminary crystallographic analysis of human Ca 2+-loaded calbindin-D28k.
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Distribution of the parvalbumin, calbindin-D28K and calretinin immunoreactivity in globus pallidus of the Brazilian short-tailed opossum (Monodelphis domestica).
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This study describes the topography, borders and divisions of the globus pallidus in the Brazilian short-tailed opossum (Monodelphis domestica) and distribution of the three calcium binding proteins, parvalbumin (PV), calbindin D-28k (CB) and calretinin (CR) in that nucleus. The globus pallidus of the opossum consists of medial and lateral parts that are visible with Nissl or Timm's staining and also in PV and CR immunostained sections. Neurons of the globus pallidus expressing these proteins were classified into three types on the basis of size and shape of their soma and dendritic tree. Type 1 neurons had medium-sized fusiform soma with dendrites sprouting from the opposite poles. Neurons of the type 2 had medium-to-large, multipolar soma with scarce, thin dendrites. Cell bodies of type 3 neurons were small and either ovoid or round. Immunostaining showed that the most numerous were neurons expressing PV that belonged to all three types. Density of the PV-immunopositive fibers and puncta correlated with the density of the PV-labeled neurons. Labeling for CB resulted mainly in the light staining of neuropil in both parts of the nucleus, while the CB-expressing cells (mainly of the type 2) were scarce and placed only along the border of the globus pallidus and putamen. Staining for calretinin resulted in labeling almost exclusively the immunoreactive puncta and fibers that were distributed with medium-to-high density throughout the nucleus. Close to the border of globus pallidus with the putamen these fibers (probably dendrites) were long, thin and varicous, while more medially bundles of thick, short and smooth fibers predominated. Single CR-ir neurons (all of the type 3) were scattered through the globus pallidus. Colocalization of two calcium binding proteins in one neuron was. never observed. The CB-ir puncta (probably terminals of axons projecting to the nucleus) frequently formed basket-like structures around the PV-ir neurons. Therefore, the globus pallidus in the opossum, much as that in the rat, consists of a heterogeneous population of neurons, probably playing diversified functions. (+info)
Proliferative and degenerative changes in striatal spiny neurons in Huntington's disease: a combined study using the section-Golgi method and calbindin D28k immunocytochemistry.
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Dysmorphic alterations of dendritic arbors and spines in spiny striatal neurons were identified in section-Golgi impregnations of moderate and severe grades of Huntington's disease (HD). These alterations could be characterized as either proliferative or degenerative changes. Proliferative changes included prominent recurving of distal dendritic segments, short-segment branching along dendrites, and increased numbers and size of dendritic spines. Degenerative alterations consisted of truncated dendritic arborizations, occasional focal dendritic swellings, and marked spine loss. Proliferative changes were found primarily in moderate grades of HD, while degenerative changes were predominantly found in severe grades. Cytopathologic changes increased with neuropathologic severity. Similar morphologic alterations were observed in calbindin D28k (Calb) stained neurons in HD striatum. The immunoreactive intensity of Calb staining was increased in the distal dendrites of positive neurons in HD striatum. The present findings provide morphologic and quantitative evidence that confirms an early and marked involvement of spiny striatal neurons in HD and suggest that neuronal growth, rather than degeneration, may be the harbinger of cell death in this disorder. (+info)