Neuronal Ca2+ sensor-1/frequenin functions in an autocrine pathway regulating Ca2+ channels in bovine adrenal chromaffin cells.
NCS-1/frequenin belongs to a family of EF-hand-containing Ca(2+) sensors expressed mainly in neurons. Overexpression of NCS-1/frequenin has been shown to stimulate neurotransmitter release but little else is known of its cellular roles. We have constructed an EF-hand mutant, NCS-1(E120Q), as a likely dominant inhibitor of cellular NCS-1 function. Recombinant NCS-1(E120Q) showed an impaired Ca(2+)-dependent conformational change but could still bind to cellular proteins. Transient expression of this mutant, but not NCS-1, in bovine adrenal chromaffin cells increased non-L-type Ca(2+) channel currents. Cells expressing NCS-1(E120Q) no longer responded effectively to the removal of autocrine purinergic/opioid inhibition of Ca(2+) currents but still showed voltage-dependent facilitation. These data are consistent with the existence of both voltage-dependent and voltage-independent pathways for Ca(2+) channel inhibition in chromaffin cells. Our results suggest a novel function for NCS-1 specific for the voltage-independent autocrine pathway that negatively regulates non-L-type Ca(2+) channels in chromaffin cells.
Weiss
J L
JL
Physiological Laboratory, University of Liverpool, Crown Street, Liverpool, L69 3BX United Kingdom.
Archer
D A
DA
Burgoyne
R D
RD
D000818:Animals; D001483:Base Sequence; D015220:Calcium Channels / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D017931:DNA Primers; D015640:Ion Channel Gating; D009419:Nerve Tissue Proteins / Q000378:metabolism / Q000502:physiology*; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides / Q000502:physiology*
D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D017931:DNA Primers; D009419:Nerve Tissue Proteins; D051580:Neuronal Calcium-Sensor Proteins; D009479:Neuropeptides; C101464:frequenin calcium sensor proteins