Reduced Delayed-Rectifier K⁺ Current in the Learning Mutant rutabaga

Abstract

In the Drosophila mutant rutabaga, short-term memory is deficient and intracellular cyclic adenosine monophosphate (cAMP) concentration is reduced. We characterized the delayed-rectifier potassium current (IK DR ) in rutabaga as compared with the wild-type. The conventional whole-cell patch-clamp technique was applied to cultured Drosophila neurons derived from embryonic neuroblasts. IK DR was smaller in rutabaga (368 ± 11 pA) than in wild-type (541 ± 14 pA) neurons, measured in a Ca 2+ -free solution. IK DR was clearly activated at ∼0 mV in the two genotypes. IK DR typically reached its peak within 10-20 msec after the start of the pulse (60 mV). There was no difference in inactivation of IK DR for wild-type (14 ± 3%) and rutabaga (19 ± 3%). After application of 10 mM TEA, in wild-type, IK DR was reduced by 46 ± 5%, whereas in rutabaga, IK DR was reduced by 28 ± 3%. Our results suggest that IK DR is carried by two different types of channels, one which is TEA-sensitive, whereas the other is TEA-insensitive. Apparently, the TEA-sensitive channel is less expressed in rutabaga neurons than in wild-type neurons. Conceivably, altered neuronal excitability in the rutabaga mutant could disrupt the processing of neural signals necessary for learning and memory.

N termini of apPDE4 isoforms are responsible for targeting the isoforms to different cellular membranes

“…For example, in Aplysia sensory neurons, overexpression of Aplysia dopamine D1-like receptor, which displays constitutive activity, changed the state of membrane excitability (Barbas et al 2006). In dunce and rutabaga, K + channel regulation or Ca 2+ dynamics within the growth cone are disrupted (Alshuaib and Mathew 2002;Berke and Wu 2002). Thus, lots of proteins were affected by chronic impairment of cAMP signaling.…”

State-Dependent Disruption of Short-Term Facilitation Due to Overexpression of the apPDE4 Supershort Form in Aplysia

“…However, several proteins were affected by the chronic impairment of cAMP signaling. For example, in dunce and rutabaga mutants, Ca 2+ dynamics within the neuronal growth cone and K + channel regulation were disrupted (Alshuaib and Mathew, 2002;Berke and Wu, 2002).…”