A Ca2+/Calmodulin-Dependent Protein Kinase ModulatesDrosophila Photoreceptor K+ Currents: A Role in Shaping the Photoreceptor Potential

Light activation of Drosophila photoreceptors leads to the generation of a depolarizing receptor potential via opening of transient receptor potential and transient receptor potential-like cationic channels. Counteracting the light-activated depolarizing current are two voltage-gated K+ conductances, IA andIK, that are expressed in these sensory neurons. Here we show that Drosophilaphotoreceptors IA andIK are regulated by calcium–calmodulin (Ca2+/calmodulin) via a Ca2+/calmodulin-dependent protein kinase (CaM kinase), with IK being far more sensitive than IA. Inhibition of Ca2+/calmodulin by N-(6 aminohexyl)-5-chloro-1-naphthalenesulfonamide or trifluoperazine markedly reduced the K+ current amplitudes. Likewise, inhibition of CaM kinases by KN-93 potently depressedIK and accelerated its C-type inactivation kinetics. The effect of KN-93 was specific because its structurally related but functionally inactive analog KN-92 was totally ineffective. In Drosophila photoreceptor mutantShKS133 , which allows isolation ofIK, we demonstrate by current-clamp recording that inhibition of IK by quinidine or tetraethylammonium increased the amplitude of the photoreceptor potential, depressed light adaptation, and slowed down the termination of the light response. Similar results were obtained when CaM kinases were blocked by KN-93. These findings place photoreceptor K+ channels as an additional target for Ca2+/calmodulin and suggest thatIK is well suited to act in concert with other components of the signaling machinery to sharpen light response termination and fine tune photoreceptor sensitivity during light adaptation.

[1]  R. Hardie.  INDO-1 Measurements of Absolute Resting and Light-Induced Ca2+ Concentration in DrosophilaPhotoreceptors , 1996, The Journal of Neuroscience.

[2]  Roger C. Hardie,et al.  Novel potassium channels encoded by the Shaker locus in drosophila photoreceptors , 1991, Neuron.

[3]  H. Lester,et al.  The inward rectifier potassium channel family , 1995, Current Opinion in Neurobiology.

[4]  L. Salkoff,et al.  Genetic analysis of Drosophila neurons: Shal, Shaw, and Shab encode most embryonic potassium currents , 1995, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[5]  H. Tokumitsu,et al.  KN-62, 1-[N,O-bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazi ne, a specific inhibitor of Ca2+/calmodulin-dependent protein kinase II. , 1990, The Journal of biological chemistry.

[6]  W. Stühmer,et al.  Molecular basis of altered excitability in Shaker mutants of Drosophila melanogaster. , 1990, The EMBO journal.

[7]  S. Goldstein,et al.  ORK1, a potassium-selective leak channel with two pore domains cloned from Drosophila melanogaster by expression in Saccharomyces cerevisiae. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[8]  M. Bate,et al.  Development of larval muscle properties in the embryonic myotubes of Drosophila melanogaster , 1993, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[9]  Y. Zhong,et al.  Modulation of different K+ currents in Drosophila: a hypothetical role for the Eag subunit in multimeric K+ channels , 1993, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[10]  R. Wyman,et al.  Genetic modification of potassium channels in Drosophila Shaker mutants , 1981, Nature.

[11]  M. Tanouye,et al.  Molecular characterization of Shaker, a Drosophila gene that encodes a potassium channel , 1987, Cell.

[12]  Xinjing Wang,et al.  The seizure Locus Encodes the DrosophilaHomolog of the HERG Potassium Channel , 1997, The Journal of Neuroscience.

[13]  T. Soderling.  Structure and regulation of calcium/calmodulin-dependent protein kinases II and IV. , 1996, Biochimica et biophysica acta.

[14]  B. Minke,et al.  The roles of trp and calcium in regulating photoreceptor function in Drosophila , 1996, Current Opinion in Neurobiology.

[15]  M. Hagiwara,et al.  The newly synthesized selective Ca2+/calmodulin dependent protein kinase II inhibitor KN-93 reduces dopamine contents in PC12h cells. , 1991, Biochemical and biophysical research communications.

[16]  D. Clapham,et al.  G-protein regulation of ion channels , 1995, Current Opinion in Neurobiology.

[17]  H. Matsumoto,et al.  Calcium/Calmodulin‐Dependent Kinase II Phosphorylates Drosophila Visual Arrestin , 1997, Journal of neurochemistry.

[18]  D Sodickson,et al.  An engineered cysteine in the external mouth of a K+ channel allows inactivation to be modulated by metal binding. , 1994, Biophysical journal.

[19]  R. Drysdale,et al.  A distinct potassium channel polypeptide encoded by the Drosophila eag locus , 1991, Science.

[20]  S B Laughlin,et al.  Voltage‐activated potassium channels in blowfly photoreceptors and their role in light adaptation. , 1991, The Journal of physiology.

[21]  B. Ganetzky,et al.  Neurogenetic studies of ion channels in Drosophila. , 1992, Ion channels.

[22]  Y. Jan,et al.  Cloned potassium channels from eukaryotes and prokaryotes. , 1997, Annual review of neuroscience.

[23]  Francisco Bezanilla,et al.  Phosphorylation affects voltage gating of the delayed rectifier K+ channel by electrostatic interactions , 1990, Neuron.

[24]  L. Salkoff,et al.  The major delayed rectifier in both Drosophila neurons and muscle is encoded by Shab , 1995, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[25]  Satpal Singh,et al.  Complete separation of four potassium currents in drosophila , 1989, Neuron.

[26]  A. Means,et al.  A Signaling Complex of Ca 2 1 -Calmodulin– Dependent Protein Kinase IV and Protein Phosphatase 2A , 1998 .

[27]  O. Pongs,et al.  Shaker encodes a family of putative potassium channel proteins in the nervous system of Drosophila. , 1988, The EMBO journal.

[28]  T. Poleck,et al.  Calcium-activated, calmodulin-dependent protein kinase activity in bovine thyroid cytosol. , 1986, Biochemical and biophysical research communications.

[29]  J E Lisman,et al.  Membrane conductances of photoreceptors. , 1981, Progress in biophysics and molecular biology.

[30]  R C Hardie,et al.  Voltage-sensitive potassium channels in Drosophila photoreceptors , 1991, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[31]  C. Montell,et al.  Calmodulin regulation of light adaptation and store-operated dark current in Drosophila photoreceptors. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[32]  A. Means,et al.  A signaling complex of Ca2+-calmodulin-dependent protein kinase IV and protein phosphatase 2A. , 1998, Science.

[33]  C. Wu,et al.  Voltage clamp analysis of membrane currents in larval muscle fibers of Drosophila: alteration of potassium currents in Shaker mutants , 1985, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[34]  C. Zuker,et al.  Calmodulin Regulation of Drosophila Light-Activated Channels and Receptor Function Mediates Termination of the Light Response In Vivo , 1997, Cell.

[35]  C. Zuker,et al.  Lights out: deactivation of the phototransduction cascade. , 1997, Trends in biochemical sciences.

[36]  D. Baylor,et al.  How photons start vision. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[37]  R. Hardie,et al.  Serotonin modulates the voltage dependence of delayed rectifier and Shaker potassium channels in drosophila photoreceptors , 1995, Neuron.

[38]  C. Zuker,et al.  The biology of vision of Drosophila. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[39]  L. Salkoff,et al.  Surfing the DNA databases for K+ channels nets yet more diversity , 1995, Neuron.

[40]  M. Bownes,et al.  Staging the metamorphosis of Drosophila melanogaster. , 1981, Journal of embryology and experimental morphology.

[41]  R. Hardie,et al.  Phosphoinositide-mediated phototransduction in Drosophila photoreceptors: the role of Ca2+ and trp. , 1995, Cell calcium.

[42]  徳光 浩.  KN-62, 1-[N,O-Bis(5-isoquinolinesulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperazine, a specific inhibitor of Ca[2+]/calmodulin-dependent protein kinase II , 1991 .

[43]  J. Lisman,et al.  Ca2+/calmodulin-binding peptides block phototransduction in Limulus ventral photoreceptors: evidence for direct inhibition of phospholipase C. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[44]  B. Rudy,et al.  Diversity and ubiquity of K channels , 1988, Neuroscience.

[45]  J. Warmke,et al.  The Drosophila erg K+ Channel Polypeptide Is Encoded by the Seizure Locus , 1997, The Journal of Neuroscience.

[46]  O. Pongs.  Molecular biology of voltage-dependent potassium channels. , 1992, Physiological reviews.

[47]  R. Payne,et al.  The light response of drosophila photoreceptors is accompanied by an increase in cellular calcium: Effects of specific mutations , 1994, Neuron.

[48]  C. Montell,et al.  Calmodulin Regulation of Calcium Stores in Phototransduction of Drosophila , 1997, Science.

[49]  H. Schulman,et al.  The multifunctional calcium/calmodulin-dependent protein kinase: from form to function. , 1995, Annual review of physiology.

[50]  C. Zuker,et al.  Signal transduction in Drosophila photoreceptors. , 1995, Annual review of neuroscience.

[51]  W. Pak,et al.  Phosrestin I undergoes the earliest light-induced phosphorylation by a calcium/calmodulin-dependent protein kinase in drosophila photoreceptors , 1994, Neuron.

[52]  O. Pongs,et al.  Frequency-Dependent Inactivation of Mammalian A-Type K+ Channel KV1.4 Regulated by Ca2+/Calmodulin-Dependent Protein Kinase , 1997, The Journal of Neuroscience.

[53]  Y. Jan,et al.  Sequence of a probable potassium channel component encoded at Shaker locus of Drosophila. , 1987, Science.

[54]  B. Hille.  Ionic channels of excitable membranes , 2001 .

[55]  T Hoshi,et al.  Biophysical and molecular mechanisms of Shaker potassium channel inactivation , 1990, Science.

[56]  R. Pearson,et al.  Protein kinase phosphorylation site sequences and consensus specificity motifs: tabulations. , 1991, Methods in enzymology.

[57]  J. Lisman,et al.  Functional significance of voltage-dependent conductances in Limulus ventral photoreceptors , 1982, The Journal of general physiology.