Modulation of neurotransmitter release by dihydropyridine-sensitive calcium channels involves tyrosine phosphorylation

TY - JOUR

T1 - Modulation of neurotransmitter release by dihydropyridine-sensitive calcium channels involves tyrosine phosphorylation

AU - Evans, G J O

AU - Pocock, J M

PY - 1999/1

Y1 - 1999/1

N2 - Cultured rat cerebellar granule cells depolarized by high KCI, display a large component of Ca2+ influx through L-type voltage-dependent Ca2+ channels as defined by a sensitivity to 1 mu M nifedipine. This Ca2+ influx is not coupled to neurotransmitter exocytosis but has implications for neuronal development. KCI stimulation in the absence of external Ca2+ followed by the readdition of Ca2+ allows the coupling of a class of L-type Ca2+ channels to neurotransmitter exocytosis as assessed by loading of glutamatergic pools with [H-3]-D-aspartate. KCI stimulation in the absence of external Ca2+ ('predepolarization') enhances tyrosine phosphorylation of several cellular proteins, and inhibitors of tyrosine kinases block both phosphorylation and the neurotransmitter release coupled to the L-type Ca2+ channel. More specifically, an inhibitor of src family tyrosine kinases, PP1, blocks the effects of predepolarization suggesting a role for a src family kinase in the process. Furthermore, L-type Ca2+ channel recruitment and modulation of release could be activated with the tyrosine phosphatase inhibitor sodium orthovanadate. The phosphoproteins enhanced by predepolarization, which include the cytoskeletal proteins focal adhesion kinase (FAK) and vinculin, are also highly phosphorylated early on in culture when neurite outgrowth occurs. As the neurons develop a network of neurites, both tyrosine phosphorylation and L-type Ca2+ channel activity decrease. These results show a novel mechanism for the recruitment of L-type Ca2+ channels and their coupling to neurotransmitter release which involves tyrosine phosphorylation. This phenomenon has a role in cerebellar granule cell development.

AB - Cultured rat cerebellar granule cells depolarized by high KCI, display a large component of Ca2+ influx through L-type voltage-dependent Ca2+ channels as defined by a sensitivity to 1 mu M nifedipine. This Ca2+ influx is not coupled to neurotransmitter exocytosis but has implications for neuronal development. KCI stimulation in the absence of external Ca2+ followed by the readdition of Ca2+ allows the coupling of a class of L-type Ca2+ channels to neurotransmitter exocytosis as assessed by loading of glutamatergic pools with [H-3]-D-aspartate. KCI stimulation in the absence of external Ca2+ ('predepolarization') enhances tyrosine phosphorylation of several cellular proteins, and inhibitors of tyrosine kinases block both phosphorylation and the neurotransmitter release coupled to the L-type Ca2+ channel. More specifically, an inhibitor of src family tyrosine kinases, PP1, blocks the effects of predepolarization suggesting a role for a src family kinase in the process. Furthermore, L-type Ca2+ channel recruitment and modulation of release could be activated with the tyrosine phosphatase inhibitor sodium orthovanadate. The phosphoproteins enhanced by predepolarization, which include the cytoskeletal proteins focal adhesion kinase (FAK) and vinculin, are also highly phosphorylated early on in culture when neurite outgrowth occurs. As the neurons develop a network of neurites, both tyrosine phosphorylation and L-type Ca2+ channel activity decrease. These results show a novel mechanism for the recruitment of L-type Ca2+ channels and their coupling to neurotransmitter release which involves tyrosine phosphorylation. This phenomenon has a role in cerebellar granule cell development.

KW - cerebellar granule cell

KW - development

KW - rat

KW - tyrosine kinase

KW - CEREBELLAR GRANULE CELLS

KW - TRANSMITTER GLUTAMATE RELEASE

KW - ISOLATED NERVE-TERMINALS

KW - FOCAL ADHESION KINASE

KW - OMEGA-AGA-IVA

KW - PROTEIN-KINASE

KW - FUNCTIONAL EXPRESSION

KW - HIPPOCAMPAL-NEURONS

KW - ALPHA-1 SUBUNIT

KW - CA2+ CHANNELS

M3 - Article

SN - 0953-816X

VL - 11

SP - 279

EP - 292

JO - The European Journal of Neuroscience

JF - The European Journal of Neuroscience

IS - 1

ER -