Synaptic activity‐related classical protein kinase C isoform localization in the adult rat neuromuscular synapse

Abstract

Protein kinase C (PKC) is essential for signal transduction in a variety of cells, including neurons and myocytes, and is involved in both acetylcholine release and muscle fiber contraction. Here, we demonstrate that the increases in synaptic activity by nerve stimulation couple PKC to transmitter release in the rat neuromuscular junction and increase the level of alpha, betaI, and betaII isoforms in the membrane when muscle contraction follows the stimulation. The phosphorylation activity of these classical PKCs also increases. It seems that the muscle has to contract in order to maintain or increase classical PKCs in the membrane. We use immunohistochemistry to show that PKCalpha and PKCbetaI were located in the nerve terminals, whereas PKCalpha and PKCbetaII were located in the postsynaptic and the Schwann cells. Stimulation and contraction do not change these cellular distributions, but our results show that the localization of classical PKC isoforms in the membrane is affected by synaptic activity.

The novel protein kinase C epsilon isoform at the adult neuromuscular synapse: location, regulation by synaptic activity-dependent muscle contraction through TrkB signaling and coupling to ACh release

“…The results show that nPKCε protein almost completely disappear after 1 day of denervation (ratio denervated/control 0.11 ± 0.08, p < 0.05) indicating that the most part of nPKCε is located in the nerve (Figure 2D). By contrast, cPKCα, an isoform ubiquitously located [25], slightly decreased (Figure 2D). Syntaxin has been used as a control of denervation.…”

“…Synaptic function of PKC family has been shown to be regulated by activity [25], so we tested whether nPKCε synaptic level is modulated by synaptic activity. Therefore, we studied whether there was any change in the amount of nPKCε and its phosphorylated form in the synaptic membrane after electrical stimulation (with and without muscle contraction).…”

“…Because the synaptic function of PKC family is regulated by activity [25], we investigated whether synaptic activity regulates the translocation to the synaptic membrane of nPKCε and its phosphorylated form (which is an indication of its activation). Furthermore, because it has been reported that electrical stimulation-induced contraction increases the translocation of PKC to the membrane [25,41-43], we also wanted to study separately the effect on nPKCε of the presynaptic stimulation and synaptic transmission from the possible effect of the muscle cell contraction.…”

“…Furthermore, because it has been reported that electrical stimulation-induced contraction increases the translocation of PKC to the membrane [25,41-43], we also wanted to study separately the effect on nPKCε of the presynaptic stimulation and synaptic transmission from the possible effect of the muscle cell contraction. Our results suggest that nPKCε has a role in some activity-related mechanism at the NMJ, and that muscle activity has an important impact on it.…”

Motor Deficit in a Tauopathy Model Is Induced by Disturbances of Axonal Transport Leading to Dying-Back Degeneration and Denervation of Neuromuscular Junctions

“…13,14 A minimum of 100 junctions was analyzed for each animal (n Z 3). The innervation status of motor endplates was assessed after labeling with the synaptophysin antibody and BTX by classifying the synaptophysin distribution into three categories: i) perfect superposition of 15 The innervation status of NMJ was also assessed after labeling with NF and BTX by categorizing them as innervated if there was any overlap between the two labels or denervated if NF was completely absent at the synaptic junction.…”