Peripheral and orofacial pain sensation is unaffected by the loss of p39

Abstract

Cdk5 is a key neuronal kinase necessary for proper brain development, which has recently been implicated in modulating nociception. Conditional deletion of Cdk5 in pain-sensing neurons attenuates pain responses to heat in both the periphery and orofacial regions. Cdk5 activity is regulated by binding to the activators p35 and p39, both of which possess a cyclin box. Our previous examination of the nociceptive role of the well-characterized Cdk5 activator p35 using mice that either lack or overexpress this regulatory subunit demonstrated that Cdk5/p35 activity affects mechanical, chemical, and thermal nociception. In contrast, the nociceptive role of Cdk5’s other less-studied activator p39 is unknown. Here, we report that the knockout of p39 in mice did not affect orofacial and peripheral nociception. The lack of any algesic response to nociceptive stimuli in the p39 knockout mice contrasts with the hypoalgesic effects that result from the deletion of p35. Our data demonstrate different and nonoverlapping roles of Cdk5 activators in the regulation of orofacial as well as peripheral nociception with a crucial role for Cdk5/p35 in pain signaling.

Nociceptive signaling through transient receptor potential vanilloid 1 is regulated by Cyclin Dependent Kinase 5-mediated phosphorylation of T407 in vivo

“…Although Cdk5 is ubiquitously expressed, its activity is primarily limited to neurons because of the restricted expression of its two activators. Cdk5/p39 activity has no effect on pain, 24 whereas the expression levels of p35 can, in contrast, modulate basal pain behavioral responses in mice. 2 , 10 , 17 Importantly, p35 expression is induced downstream of inflammation, particularly through sustained ERK1/2 activation via inflammatory mediators such as nerve growth factor and tumor necrosis factor-α.…”

“…DNA sequencing (NIDCR Sequencing Core) was performed using a 5 ′ -agagggagatccacgaacca-3 ′ forward primer to further verify the T407A knock-in point mutation within the Trpv1 gene ( Figure 1c ). Quantitative real-time PCR was performed as described in Prochazkova et al 24 using Assays on Demand TaqMan primers for TRPV1 and GAPDH (Applied Biosystems, Foster City, CA, USA). Real-time PCR was run in duplicate on a 7500 Real-time PCR System (Applied Biosystems, Foster City, CA), where TRPV1 expression levels were normalized to the levels of GAPDH using the comparative cycle threshold (Ct) method ( Figure 2a ).…”

Protocols for Characterization of Cdk5 Kinase Activity

“…Ablation of Cdk5 leads to embryonic lethality (Ohshima et al, 1996), while p35-/-mice are viable but still display cortical layering defects (Chae et al, 1997, Ohshima et al, 2001. The p39-/-mice, however, show no observable phenotypic neurological defects and no significant decrease in Cdk5 activity in neuronal tissues such as the brain and trigeminal ganglia (Ko et al, 2001;Prochazkova et al, 2017). Compound deletion of both p35 and p39 is needed to fully replicate the phenotype of the Cdk5 knockout mice.…”

“…The expression of p35 begins during early embryonic stages and peaks in neonates, with its expression generally highest in the cerebral cortex and hippocampus. In contrast, p39 expression appears postnatally and is mainly localized to the cerebellum (Prochazkova et al., 2017). The expression levels of the Cdk5 activators are the rate‐limiting step for Cdk5 enzymatic activity, as the transgenic overexpression of Cdk5 in mice did not alter overall neuronal kinase activity, but overexpression of the p35 resulted in increased kinase activity (Takahashi et al., 2005).…”