An invertebrate calcium-binding protein of the calbindin subfamily: protein structure, genomic organization, and expression pattern of the calbindin-32 gene of Drosophila

Abstract

Antisera against vertebrate calcium-binding proteins cross-react with Drosophila nervous and muscle tissue. We have used an antiserum against carp parvalbumin to isolate from a Drosophila head cDNA library immunopositive expression clones. Tissue in situ hybridization identified a clone that labeled specific neurons and muscles similar to the parvalbumin-like immunohistochemical staining pattern. Five independent cDNAs derive from an mRNA whose open reading frame codes for a 310 amino acid polypeptide. Sequence analysis identifies six EF-hand calcium-binding domains and reveals 42% and 37% homology to chicken calretinin and calbindin D-28k, respectively. Since the positions of 9 out of 10 introns within the ORF are conserved from the Drosophila gene to both vertebrate genes, we conclude that we have identified the first invertebrate member of the calbindin sub-family of calcium-binding protein genes of the EF-hand homolog family. The calbindin-32 gene (cbn) maps to 53E on the second chromosome. It is expressed through most of ontogenesis with a selective distribution in the nervous system and in a few small adult thoracic muscles. The cloning of a Drosophila homolog to vertebrate neuronal Ca(2+)-binding proteins opens new routes to study the so far largely elusive function of these brain molecules.

Calcium-Binding Proteins in the Central Nervous System.

“…There may be more cell-type specific EF-hand proteins which may reflect the calcium-related characteristics of subset cells containing them. An invertebrate homologue of CB, calbindin 32 was recently discovered in drosophila (83), which may help to elucidate the function(s) of CB. How they are expressed in distinct cell populations and how they function under neuron-neuron and neuron-glia interaction not only in the adult but also during the development or in the experimental or pathological states must be determined to understand the nervous system.…”

Ataxia and altered dendritic calcium signaling in mice carrying a targeted null mutation of the calbindin D28k gene

“…It was originally purified from chicken intestine (3), and it is also expressed in kidney, where it is thought to facilitate transport of calcium across cells (4). Later, it was found to be expressed throughout the nervous system (5) in species ranging from invertebrates to mammals (6). In the mature nervous system, calbindin D28k expression is predominantly neuronal, and this protein has been found in long axon neurons, such as thalamic and striatonigral projection neurons, cerebellar Purkinje cells, and sensory neurons, and in short axon neurons, such as interneurons in the spinal cord, cerebral cortex, and hippocampus as well as dentate granule cells (1,5,(7)(8)(9)(10).…”

Calbindin and calretinin immunoreactivities in the retina of a chondrostean, Acipenser baeri

“…Thus, whether the presence of CB and/or CR in neurons is linked to the presence of some types of cell organelle, channel or receptor in retinal cells remains to be determined. Finally, only a single CB-like protein has been reported to date in squid and Drosophila (Christakos et al 1987;Reifegerste et al 1993). The finding, by Western blot and immunocytochemistry, of both CB and CR in sturgeon, together with the immunocytochemical results of Dalil-Thiney et al (1995) in lamprey, indicates that CR and CB peptides appeared early in vertebrate lines.…”