TY - JOUR
T1 - Homer 1a enhances spike-induced calcium influx via L-type calcium channels in neocortex pyramidal cells
AU - Yamamoto, Kenji
AU - Sakagami, Yu
AU - Sugiura, Shigeki
AU - Inokuchi, Kaoru
AU - Shimohama, Shun
AU - Kato, Nobuo
PY - 2005/9
Y1 - 2005/9
N2 - The scaffold protein family Homer/Vesl serves to couple surface receptors or channels with endoplasmic calcium release channels. Homer 1a/Vesl-1S is regarded as regulating such coupling in an activity-dependent manner. The present calcium photometry and electrophysiological measurement revealed that Homer 1a up-regulates voltage-dependent calcium channels (VDCCs), depending on inositol-1,4,5-trisphosphate (IP3) receptors (IP3Rs). In rat neocortex pyramidal cells, intracellular injection by diffusion from the patch pipette (referred to as 'infusion') of Homer 1a protein enhanced spike-induced calcium increase, depending on both the protein concentration and spike frequency. Induction of this enhancement was disrupted by blockers of key molecules of the mGluR-IP3 signalling pathway, including metabotropic glutamate receptors (mGluRs), phospholipase C and IP3Rs. However, infusion of IP3 failed to mimic the effect of Homer 1a, suggesting requirement for a second Homer 1a-mediated signalling as well as the mGluR-IP3 signalling. In contrast to the induction, maintenance of this enhancement was independent of the mGluR-IP3 signalling, taking the form of augmented calcium influx via L-type VDCCs. Presumably due to the VDCC up-regulation, threshold currents for calcium spikes were reduced. Given that Homer 1a induction is thought to down-regulate neural excitability and hence somatic spike firing, this facilitation of calcium spikes concomitant with such attenuated firing may well have a critical impact on bi-directional synaptic plasticity.
AB - The scaffold protein family Homer/Vesl serves to couple surface receptors or channels with endoplasmic calcium release channels. Homer 1a/Vesl-1S is regarded as regulating such coupling in an activity-dependent manner. The present calcium photometry and electrophysiological measurement revealed that Homer 1a up-regulates voltage-dependent calcium channels (VDCCs), depending on inositol-1,4,5-trisphosphate (IP3) receptors (IP3Rs). In rat neocortex pyramidal cells, intracellular injection by diffusion from the patch pipette (referred to as 'infusion') of Homer 1a protein enhanced spike-induced calcium increase, depending on both the protein concentration and spike frequency. Induction of this enhancement was disrupted by blockers of key molecules of the mGluR-IP3 signalling pathway, including metabotropic glutamate receptors (mGluRs), phospholipase C and IP3Rs. However, infusion of IP3 failed to mimic the effect of Homer 1a, suggesting requirement for a second Homer 1a-mediated signalling as well as the mGluR-IP3 signalling. In contrast to the induction, maintenance of this enhancement was independent of the mGluR-IP3 signalling, taking the form of augmented calcium influx via L-type VDCCs. Presumably due to the VDCC up-regulation, threshold currents for calcium spikes were reduced. Given that Homer 1a induction is thought to down-regulate neural excitability and hence somatic spike firing, this facilitation of calcium spikes concomitant with such attenuated firing may well have a critical impact on bi-directional synaptic plasticity.
KW - Calcium channels
KW - Calcium influx
KW - Electroconvulsive shock
KW - Glutamate receptor
KW - Rat
KW - Scaffold protein
UR - http://www.scopus.com/inward/record.url?scp=26644433414&partnerID=8YFLogxK
U2 - 10.1111/j.1460-9568.2005.04278.x
DO - 10.1111/j.1460-9568.2005.04278.x
M3 - 学術論文
C2 - 16190889
AN - SCOPUS:26644433414
SN - 0953-816X
VL - 22
SP - 1338
EP - 1348
JO - European Journal of Neuroscience
JF - European Journal of Neuroscience
IS - 6
ER -