Phosphorylation of the Ca2+-binding protein CaBP4 by protein kinase C zeta in photoreceptors

• Published in: The Journal of neuroscience Vol. 27; no. 46; pp. 12743 - 12754
• Main Authors: Lee, Amy, Jimenez, Amber, Cui, Guiying, Haeseleer, Françoise
• Format: Journal Article
• Language: English
• Published: United States Society for Neuroscience 14.11.2007
• Subjects: Adaptation, Ocular - genetics; Amino Acid Substitution - genetics; Animals; Binding Sites - genetics; Binding Sites - radiation effects; Calcium - metabolism; Calcium Channels, L-Type - metabolism; Calcium Signaling - genetics; Calcium Signaling - radiation effects; Calcium-Binding Proteins - genetics; Calcium-Binding Proteins - metabolism; Membrane Potentials - genetics; Mice; Mice, Inbred C57BL; Mice, Knockout; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Phosphorylation - radiation effects; Photic Stimulation; Photoreceptor Cells, Vertebrate - cytology; Photoreceptor Cells, Vertebrate - metabolism; Photoreceptor Cells, Vertebrate - radiation effects; Protein Kinase C - genetics; Protein Kinase C - metabolism; Retina - cytology; Retina - metabolism; Serine - genetics; Serine - metabolism; Vision, Ocular - genetics; Vision, Ocular - radiation effects
• ISSN: 1529-2401; 0270-6474; 1529-2401
• DOI: 10.1523/JNEUROSCI.4264-07.2007

CaBP4 is a calmodulin-like neuronal calcium-binding protein that is crucial for the development and/or maintenance of the cone and rod photoreceptor synapse. Previously, we showed that CaBP4 directly regulates Ca(v)1 L-type Ca2+ channels, which are essential for normal photoreceptor synaptic transmission. Here, we show that the function of CaBP4 is regulated by phosphorylation. CaBP4 is phosphorylated by protein kinase C zeta (PKCzeta) at serine 37 both in vitro and in the retina and colocalizes with PKCzeta in photoreceptors. CaBP4 phosphorylation is greater in light-adapted than dark-adapted mouse retinas. In electrophysiological recordings of cells transfected with Ca(v)1.3 and CaBP4, mutation of the serine 37 to alanine abolished the effect of CaBP4 in prolonging the Ca2+ current through Ca(v)1.3 channel, whereas inactivating mutations in the CaBP4 Ca2+-binding sites strengthened Ca(v)1.3 modulation. These findings demonstrate how light-stimulated changes in CaBP4 phosphorylation and Ca2+ binding may regulate presynaptic Ca2+ signals in photoreceptors.