calbindinD28k

Calbindin-D28k is a cytosolic calcium-binding protein of the EF-hand family. It is a 28-kilodalton protein encoded by the CALB1 gene in humans. Calbindin-D28k binds calcium ions with moderate affinity and functions primarily as an intracellular calcium buffer and regulator of calcium signaling in neurons.

Within the mammalian brain, calbindin-D28k is expressed in specific neuronal populations, most notably Purkinje cells of the cerebellum and a subset of hippocampal and cortical interneurons. Its distribution is used in neuroanatomy as a marker to distinguish certain neuron types and circuits.

Its calcium-buffering capacity helps shape calcium transients that underlie neurotransmitter release, synaptic plasticity, and the activation of calcium-dependent enzymes and transcription pathways. By constraining intracellular calcium elevations, calbindin-D28k can contribute to neuronal resistance against calcium-mediated excitotoxicity under stress.

Clinically, changes in calbindin-D28k expression have been observed in aging and in several neurological disorders, including Alzheimer’s disease and other neurodegenerative conditions, though the functional consequences remain an area of active research. In the laboratory, calbindin-D28k serves as a tool for identifying specific neuron subtypes and studying calcium homeostasis and neuroprotection in model systems.