Protein kinase C gamma-mediated phosphorylation of GluA1 in the postsynaptic density of spinal dorsal horn neurons accompanies neuropathic pain, and dephosphorylation by calcineurin is associated with prolonged analgesia

Abstract

Loss of calcineurin (protein phosphatase 3) activity and protein content in the post-synaptic density (PSD) of spinal dorsal horn neurons was associated with pain behavior following chronic constriction injury (CCI) of the rat sciatic nerve, and intrathecal administration of the phosphatase provided prolonged analgesia (Miletic et al., Pain 2013;154:2024-2033). In this study we examined if one consequence of the loss of calcineurin was the persistent phosphorylation of the GluA1 subunit of α-amino-3-hydroxy-5-methyl-4-isoxazolepropioinic acid receptors (AMPAR) in the PSD. This would allow continual activation of AMPAR at the synapse to help maintain a long-lasting enhancement of synaptic function, i.e., neuropathic pain. We also investigated if the phosphorylation was mediated by protein kinase A (PKA), protein kinase C gamma (PKCγ) or calcium-calmodulin dependent kinase II (CaMKII), and if the prolonged calcineurin analgesia was associated with GluA1 dephosphorylation. Mechanical thresholds and thermal latencies were obtained before CCI. Seven days later the behavioral testing was repeated before saline, calcineurin or the specific peptide inhibitors of PKA (PKI-tide), PKCγ (PKC 19-31) or CaMKII (AIP-2) were injected intrathecally. The behavior was retested before the animals were euthanized and their PSD isolated. All CCI animals developed mechanical and thermal hypersensitivity. This was associated with phosphorylation of GluA1 in the ipsilateral PSD at Ser831 (but not Ser845) by PKCγ and not by PKA or CaMKII. Intrathecal treatment with calcineurin provided prolonged analgesia and this was accompanied by GluA1 dephosphorylation. Therapy with calcineurin may prove useful in the prolonged clinical management of well-established neuropathic pain.

Molecular Understanding of the Activation of CB1 and Blockade of TRPV1 Receptors: Implications for Novel Treatment Strategies in Osteoarthritis

“…Furthermore, recent research revealed that H89, a PKA (encoded by the Prkaca gene) inhibitor and GF109203X, a PKCγ (encoded by the Prkcg gene) inhibitor suppresses TRPV1 externalization in DRGs sensory neuron cultures [ 35 ] and that the latter compound is also able to reverse capsaicin-induced pain-related behaviour in MIA rats [ 36 ]. Decreases of Mapk14 and Prkcg mRNA levels following FAAH inhibition highlights hopes for new treatment strategies of neuropathic components in rheumatic diseases, as seen with intrathecal administration of p38α MAPK and PKCγ inhibitors in a chronic constriction injury model of neuropathic pain [ 37 , 38 ].…”

Calcium Signaling, PKC Gamma, IP3R1 and CAR8 Link Spinocerebellar Ataxias and Purkinje Cell Dendritic Development

“…This suggests that PKC-mediated phosphorylation of the IP 3 R1 may form part of a positive feedback loop. Activated PKCγ phosphorylates TRPC3-channels which reduces Ca 2+ influx from the plasma membrane through these channels and limits the Ca 2+ concentration in the cytoplasm [ 29 , 87 ]. As discussed above, one mutation related to SCA14 was recently shown to result in a constitutive active form of PKCγ causing abnormal dendritic development of Purkinje cells linking an increased PKC activity to the pathogenesis of ataxia [ 45 ].…”

Spinal PKCα inhibition and gene-silencing for pain relief: AMPAR trafficking at the synapses between primary afferents and sensory interneurons

“…The molecular mechanism of PKCα-dependent upregulation of CP-AMPARs includes the activation of PKCα under painful conditions as an upstream trigger for the AMPAR protein phosphorylation, a subsequent disrupting of the receptor binding to its synaptic anchoring protein, followed by receptor’s internalization 5 . Multiple sites for the PKC-mediated phosphorylation of AMPAR subunits have been distinguished: serine residue S880 for GluA2 5 , S831 27 , S818, and S816 for GluA1 28 – 30 that opens considerations for multiple involvement of different PKC enzyme isoforms in both inflammatory pain development and maintenance.…”