Details

Autor(en) / Beteiligte

• Wykes, Robert CE
• Bauer, Claudia S
• Khan, Saeed U
• Weiss, Jamie L
• Seward, Elizabeth P

Titel

Differential Regulation of Endogenous N- and P/Q-Type Ca super(2+) Channel Inactivation by Ca super(2+)/Calmodulin Impacts on Their Ability to Support Exocytosis in Chromaffin Cells

Ist Teil von

• The Journal of neuroscience, 2007-05, Vol.27 (19), p.5236-5248

Erscheinungsjahr

2007

Quelle

Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals

Beschreibungen/Notizen

• P/Q-type (Ca sub(V)2.1) and N-type (Ca sub(V)2.2) Ca super(2+) channels are critical to stimulus-secretion coupling in the nervous system; feedback regulation of these channels by Ca super(2+) is therefore predicted to profoundly influence neurotransmission. Here we report divergent regulation of Ca super(2+)-dependent inactivation (CDI) of native N- and P/Q-type Ca super(2+) channels by calmodulin (CaM) in adult chromaffin cells. Robust CDI of N-type channels was observed in response to prolonged step depolarizations, as well as repetitive stimulation with either brief step depolarizations or action potential-like voltage stimuli. Adenoviral expression of Ca super(2+)-insensitive calmodulin mutants eliminated CDI of N-type channels. This is the first demonstration of CaM-dependent CDI of a native N-type channel. CDI of P/Q-type channels was by comparison modest and insensitive to expression of CaM mutants. Cloning of the C terminus of the Ca sub(V)2.1 alpha 1 subunit from chromaffin cells revealed multiple splice variants lacking structural motifs required for CaM-dependent CDI. The physiological relevance of CDI on stimulus-coupled exocytosis was revealed by combining perforated-patch voltage-clamp recordings of pharmacologically isolated Ca super(2+) currents with membrane capacitance measurements of exocytosis. Increasing stimulus intensity to invoke CDI resulted in a significant decrease in the exocytotic efficiency of N-type channels compared with P/Q-type channels. Our results reveal unexpected diversity in CaM regulation of native Ca sub(V)2 channels and suggest that the ability of individual Ca super(2+) channel subtypes to undergo CDI may be tailored by alternative splicing to meet the specific requirements of a particular cellular function.