Effects of Caveolin-1 on the Na+-Ca2+ Exchanger Activity in Soma of Rat Cerebellar Purkinje Neurons

초록

The physiological activity of sodium calcium exchange (NCX) plays an important role in Ca2+ mechanisms such as long-term depression (LTD) induction in cerebellar Purkinje neurons. NCX has special amino acid sequences for binding with caveolin. NCX-caveolin complex implicates that caveolin may be serve as a regulator of NCX activity. To investigate this question, the NCX activity was investigated by measurements of Ca2+ influx and efflux via NCX under inhibitory condition of caveolin-1 synthesis. It was founded that caveolin-1 is expressed throughout the soma of Purkinje neuron, and the immunoreactivity of caveolin-3 was faintly expressed, whereas that of caveolin-2 was not detected. After treatments of antisense oligoneucleotides against caveolin-1 for 24 hours, resting levels of [Ca2+]i are significantly higher in Purkinje neurons treated with caveolin-1 antisense oligoneucleotides (1.52 ± 0.15 vs. 0.70 ± 0.03, P<0.001) than those in neurons untreated. In caveolin-1 antisense oligoneucleotides treated neurons, Ca2+ influx via reverse mode of NCX elicited by Na+ removal was suppressed and Ca2+ clearance via the forward mode of NCX was delayed. The amplitude of Ca2+ change measured as the difference between the peak and basal values in R340/380 was much suppressed, compared to those of the control and lipofectamine-treated neurons (0.01 vs. 0.43, 0.34; P<0.001). Rates of Ca2+ clearance (-R340/380/min) were also reduced (0.003 vs. 0.041, 0.037; P<0.001). All these findings strongly imply that caveolin-1 has a physiological role of modulating NCX activity in Purkinje neurons.