Rat Tumor type M2 Pyruvate Kinase ELISA Kit

Multiple kinase activations contribute to long-term synaptic plasticity, a cellular mechanism mediating long-term memory. The sensorimotor synapse of Aplysia expresses different forms of long-term facilitation (LTF)-nonassociative and associative LTF-that require the timely activation of kinases, including protein kinase C (PKC). It is not known which PKC isoforms in the sensory neuron or motor neuron L7 are required to sustain each form of LTF. We show that different PKMs, the constitutively active isoforms of PKCs generated by calpain cleavage, in the sensory neuron and L7 are required to maintain each form of LTF. Different PKMs or calpain isoforms were blocked by overexpressing specific dominant-negative constructs in either presynaptic or postsynaptic neurons. Blocking either PKM Apl I in L7, or PKM Apl II or PKM Apl III in the sensory neuron 2 d after 5-hydroxytryptamine (5-HT) treatment reversed persistent nonassociative LTF. In contrast, blocking either PKM Apl II or PKM Apl III in L7, or PKM Apl II in the sensory neuron 2 d after paired stimuli reversed persistent associative LTF. Blocking either classical calpain or atypical small optic lobe (SOL) calpain 2 d after 5-HT treatment or paired stimuli did not disrupt the maintenance of persistent LTF. Soon after 5-HT treatment or paired stimuli, however, blocking classical calpain inhibited the expression of persistent associative LTF, while blocking SOL calpain inhibited the expression of persistent nonassociative LTF. Our data suggest that different stimuli activate different calpains that generate specific sets of PKMs in each neuron whose constitutive activities sustain long-term synaptic plasticity.

PKM zeta has been proposed to be essential for maintenance of long-term potentiation (LTP) and long-term memory (LTM). However, recent data from PKM zeta-knockout mice has called this role into question. Instead, the other atypical isoform, protein kinase C iota/lambda (PKC iota/lambda), has emerged as a potential alternative player. Therefore, the nature of the "memory molecule'' maintaining learned information remains uncertain. Here, we report knockdown (KD) of PKC iota/lambda and PKM zeta in the dorsal hippocampus and find deficits in early expression and late maintenance, respectively, during both LTP and hippocampus-dependent LTM. Sequential increases in the active form of PKC iota/lambda and PKM zeta are detected during LTP or fear conditioning. Importantly, PKM zeta, but not PKC iota/lambda, KD disrupts previously established LTM. Thus, PKC iota/lambda and PKM zeta have distinct functions in LTP and memory, with PKM zeta playing a specific role in memory maintenance. This relaying pattern may represent a precise molecular mechanism by which atypical PKCs regulate the different stages of memory.