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ACTIVATION OF THE MITOCHONDRIAL KATP CHANNEL BY UDP A.E. Negoda1, G.D.
Mironova1, S.M. Grigoriev1, Y. Skarga1,
A.J. Kowaltowski2,3, P. Paucek2 and K.D. Garlid2
We have previously reported that a 55 kDa protein isolated from inner mitochondrial membranes forms an ATP-sensitive, potassium-selective, channel (mitoKATP) with 10 pS conductance when reconstituted into planar lipid bilayer membranes (1). As is commonly observed, these channel often reconstitute as clusters of individual channels which switch on and off simultaneously (2). The clusters show a higher open probability in the absence of ATP and are closed by physiological concentrations of ATP. In this communication we present evidence that UDP is an effective activator of the reconstituted mitoKATP channel. In our experiments, channel activity was 65-75% inhibited by 0.5 mM ATP, in a manner reversed by UDP concentrations as low as 1 mM. Total channel reactivation was observed using 25 mM UDP. UDP was also capable of rescuing "silent" channels, which lost activity due to rundown of the reconstituted protein. However, this activation required higher UDP concentrations. UTP was less effective as a mitoKATP opener. In addition to modulating reconstituted mitoKATP, UDP also reestablished K+ uptake into intact mitochondria which had previously been inhibited by ATP. This UDP-promoted reactivation was prevented by the mitoKATP inhibitor 5-hydroxydecanoate. Thus, UDP may be an important physiological regulator of the mitoKATP channel and can play a role in cardioprotection. 1) Mironova et al.
(1996) Membr. Cell Biol. 10:429-437
This study was supported by FIRCA PA-9511.
For further information contact...Carmen Mannella: carmen@wadsworth.org |
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