In the retina, Ca2+ modulation plays an important role in the conversion of the light signal received by photoreceptors into an electrical signal transmitted to the brain. In both types of photoreceptor cells, Ca2+ plays an important role in adaptation and modulates the physiological actovity of several of the biochemical events underlying phototransduction. Ca2+ also plays a role in the biochemical processes at synapses, whereit triggers the release of the neurotransmitter glutamate. Most of the Ca2+ signaling is accomplished through the interaction of Ca2+ with specific proteins directly or, more often, via Ca2+ - binding proteins. Numerous Ca2+ - binding proteins are present in neurons and are crucial players in the propagation of the Ca2+ signals critical for neuron function.

The research in my lab focuses on the characterization of neuronal calcium-binding proteins named CaBPs (CaM) (Haeseleer et al., 2002; Haeseleer and Palczewski, 2002; Haeseleer et al., 2000). My lab has identified 8 members of this subfamily of calcium - binding proteins closely related to calmodulin. The CaBP protein sequences share ~50% similarity with calmodulin. CaBP2 and 5 are retina-specific proteins. CaBP1 and CaBP8 are expressed in both retina and in brain. CaBP1, CaBP2 and CaBP5 have been shown to be capable of modulating targets known to be modulated by CaM, like G protein-coupled receptor kinase 2, CaM kinase II (Haeseleer et al., 2000), and calcineurin (ref). CaBPs are also known to be modulate calcium channels. Changes in Ca2+ concentration promotes binding of CaBPs to the N-terminus of the inositol triphosphate receptor (InsP3R), which is an ubiquitously expressed intracellular Ca2+ channel. CaBP1 has also been shown to bind to the calmodulin-binding domain of the alpha 2.1 sub-unit of the P/Q-type voltage-gated Ca2+ channel, but modulates the channel differently than does calmodulin. Studies are currently underway to determine the role of these CaBPs in CaBP-deficient mice.