TFP5, a Peptide Derived from p35, a Cdk5 Neuronal Activator, Rescues Cortical Neurons from Glucose Toxicity

Abstract

Multiple lines of evidence link the incidence of diabetes to the development of Alzheimer’s disease (AD). Patients with diabetes have a 50 to 75% increased risk of developing AD. Cyclin dependent kinase 5 (Cdk5) is a serine/threonine protein kinase, which forms active complexes with p35 or p39, found principally in neurons and in pancreatic β cells. Recent studies suggest that Cdk5 hyperactivity is a possible link between neuropathology seen in AD and diabetes. Previously, we identified P5, a truncated 24-aa peptide derived from the Cdk5 activator p35, later modified as TFP5, so as to penetrate the blood-brain barrier after intraperitoneal injections in AD model mice. This treatment inhibited abnormal Cdk5 hyperactivity and significantly rescued AD pathology in these mice. The present study explores the potential of TFP5 peptide to rescue high glucose (HG)-mediated toxicity in rat embryonic cortical neurons. HG exposure leads to Cdk5- p25 hyperactivity and oxidative stress marked by increased reactive oxygen species production, and decreased glutathione levels and superoxide dismutase activity. It also induces hyperphosphorylation of tau, neuroinflammation as evident from the increased expression of inflammatory cytokines like TNF-α, IL-1β, and IL-6, and apoptosis. Pretreatment of cortical neurons with TFP5 before HG exposure inhibited Cdk5-p25 hyperactivity and significantly attenuated oxidative stress by decreasing reactive oxygen species levels, while increasing superoxide dismutase activity and glutathione. Tau hyperphosphorylation, inflammation, and apoptosis induced by HG were also considerably reduced by pretreatment with TFP5. These results suggest that TFP5 peptide may be a novel candidate for type 2 diabetes therapy.

Peptide TFP5/TP5 derived from Cdk5 activator P35 provides neuroprotection in the MPTP model of Parkinson’s disease

“…Kinase assays were performed as described previously, with modification ( Binukumar et al ., 2014 ). Briefly, seven DIC mesencephalic neuron-glia cultures or neuron-enriched cultures were pretreated or not with TFP5 (500 nM) or scrambled peptide for 12 h and then coincubated in the presence of different concentrations of MPP+ and TFP5 or scrambled peptide for 24 h, followed by lysis in T-PER tissue protein extraction reagent (Thermo Scientific).…”

“…Western blot analysis was performed as described previously ( Binukumar et al ., 2014 ). In brief, cells or brain tissues were lysed or homogenized in extraction buffer, respectively, and centrifuged at 10,000 × g for 5 min, and supernatants were collected and protein determined.…”

“…When injected intraperitoneally into 5XFAD AD model mice, it significantly reduced Cdk5/p25 hyperactivity and hyperphosphorylated tau and rescued behavior deficits of spatial working memory and motor deficits ( Shukla et al ., 2013 ). Moreover, TFP5 also reduced toxicity in cortical neurons exposed to high glucose ( Binukumar et al ., 2014 ). We now report that intraperitoneal injection of TP5 (TFP5 without FITC) into MPTP-induced mice effectively blocks degeneration of dopamine neurons in the SNpc and almost completely prevents the loss of striatal dopamine and its metabolites.…”

TFP5 prevents 1-methyl-4-phenyl pyridine ion-induced neurotoxicity in mouse cortical neurons

“…A limitation of this study is the lack of activity measurements of Cdk5/p25 due to experimental limitations. However, the specific inhibitory effect of TFP5 on Cdk5/p25 has been well documented in the literature ( 20 , 25 ). Inflammatory factors also play an important role in the pathology of PD.…”

Computational study of the inhibitory mechanism of the kinase CDK5 hyperactivity by peptide p5 and derivation of a pharmacophore

“…In vitro and in vivo data have shown that the truncated 24-residue peptide p5 specifically reduces CDK5-p25 activity, without affecting the endogenous CDK5-p35 function in presence of certain neuron specific molecules [7, 19]. A peptide derived from p5, TFP5, has recently been shown to cross the blood brain barrier and rescue cortical neurons without causing side effects [20]. This experimental evidence shows the potential of p5-based compounds to reach the brain and selectively inhibit the CDK5-p25 activity.…”