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The Journal of Neuroscience, July 28, 2004, 24(30):6833-6841; doi:10.1523/JNEUROSCI.1694-04.2004

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Cellular/Molecular
Regulation of an Aplysia Bag Cell Neuron Cation Channel by Closely Associated Protein Kinase A and a Protein Phosphatase

Neil S. Magoski

Department of Physiology, Queen's University, Kingston, Ontario K7L 3N6, Canada

Ion channel regulation by closely associated kinases or phosphatases has emerged as a key mechanism for orchestrating neuromodulation. An exemplary case is the nonselective cation channel that drives the afterdischarge in Aplysia bag cell neurons. Initial studies showed that this channel is modulated by both a closely associated PKC and a serine/threonine protein phosphatase (PP). In excised, inside-out patches, the addition of ATP (a phosphate source) increases open probability (P_O) through PKC, and this is reversed by the PP. Previous work also reported that, in certain cases, ATP can decrease cation channel P_O. The present study characterizes and provides a mechanism for this decreased P_O ATP response. The kinetic change for channels inhibited by ATP was identical to the previously reported effect of exogenously applied protein kinase A (PKA) (i.e., a lengthening of the third closed-state time constant). The decreased P_O ATP response was blocked by the PKA inhibitor peptide PKA_6-22, and its reversal was prevented by the PP inhibitor microcystin-LR. Furthermore, PKA_6-22 did not alter the increased P_O ATP response. This suggests that both PKA and a PP are closely associated with these cation channels, but PKA and PKC are not simultaneously targeted. After an afterdischarge, the bag cell neurons are refractory and fail to respond to subsequent stimulation. The association of PKA with the cation channel may contribute to this decrease in excitability. Altering the constituents of a regulatory complex, such as exchanging PKA for PKC, may represent a general mechanism to precisely control ion channel function and excitability.

Key words: Aplysia; bag cell neurons; cation channel; phosphorylation; protein kinase A; excitability

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Received May 4, 2004; revised June 10, 2004; accepted June 14, 2004.

This article has been cited by other articles:

				A. Y. Hung and N. S. Magoski Activity-Dependent Initiation of a Prolonged Depolarization in Aplysia Bag Cell Neurons: Role for a Cation Channel J Neurophysiol, March 1, 2007; 97(3): 2465 - 2479. [Abstract] [Full Text] [PDF]

				D. A. Lupinsky and N. S. Magoski Ca2+-dependent regulation of a non-selective cation channel from Aplysia bag cell neurones J. Physiol., September 1, 2006; 575(2): 491 - 506. [Abstract] [Full Text] [PDF]

				N. S. Magoski and L. K. Kaczmarek Association/Dissociation of a Channel-Kinase Complex Underlies State-Dependent Modulation J. Neurosci., August 31, 2005; 25(35): 8037 - 8047. [Abstract] [Full Text] [PDF]

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