A 24-Residue Peptide (p5), Derived from p35, the Cdk5 Neuronal Activator, Specifically Inhibits Cdk5-p25 Hyperactivity and Tau Hyperphosphorylation

Ya-Li Zheng,Niranjana D Amin,Ya-Fang Hu,Parvathi Rudrabhatla,Varsha Shukla,Jyotshnabala Kanungo,Sashi Kesavapany,Philip Grant,Wayne Albers,Harish C Pant

doi:10.1074/jbc.m110.134643

Abstract

The activity of Cdk5-p35 is tightly regulated in the developing and mature nervous system. Stress-induced cleavage of the activator p35 to p25 and a p10 N-terminal domain induces deregulated Cdk5 hyperactivity and perikaryal aggregations of hyperphosphorylated Tau and neurofilaments, pathogenic hallmarks in neurodegenerative diseases, such as Alzheimer disease and amyotrophic lateral sclerosis, respectively. Previously, we identified a 125-residue truncated fragment of p35 called CIP that effectively and specifically inhibited Cdk5-p25 activity and Tau hyperphosphorylation induced by Aβ peptides in vitro, in HEK293 cells, and in neuronal cells. Although these results offer a possible therapeutic approach to those neurodegenerative diseases assumed to derive from Cdk5-p25 hyperactivity and/or Aβ induced pathology, CIP is too large for successful therapeutic regimens. To identify a smaller, more effective peptide, in this study we prepared a 24-residue peptide, p5, spanning CIP residues Lys(245)-Ala(277). p5 more effectively inhibited Cdk5-p25 activity than did CIP in vitro. In neuron cells, p5 inhibited deregulated Cdk5-p25 activity but had no effect on the activity of endogenous Cdk5-p35 or on any related endogenous cyclin-dependent kinases in HEK293 cells. Specificity of p5 inhibition in cortical neurons may depend on the p10 domain in p35, which is absent in p25. Furthermore, we have demonstrated that p5 reduced Aβ(1-42)-induced Tau hyperphosphorylation and apoptosis in cortical neurons. These results suggest that p5 peptide may be a unique and useful candidate for therapeutic studies of certain neurodegenerative diseases.

Highlights

The activity of Cdk5, a multifunctional serine/threonine kinase, is critical for neuronal development and synaptic activity; it sustains neurite outgrowth, neuronal migration, cortical lamination, and survival [1,2,3,4,5,6,7,8,9]
The finding that p25 may be toxic comes from studies of cortical neurons treated with ␤-amyloid (A␤), a key marker of AD pathology, where p35 is converted to p25 accompanied by activated Cdk5, Tau hyperphosphorylation, and apoptosis [22, 23]
These drugs do not act on Cdk5-p25 and inhibit Cdk5-p35 and other Cdks essential for normal development and function. This could be responsible for serious secondary side effects and thereby compromise any therapeutic value. Our approach to this problem, is based on earlier studies, where we identified a peptide of 125 amino acid residues of p35 (CIP) that inhibited Cdk5-p25 activity and rescued cortical neurons from lysates of these infected cells (from A)␤-induced apoptosis without affecting Cdk5-p35 activity [27]

Summary

Introduction

The activity of Cdk5, a multifunctional serine/threonine kinase, is critical for neuronal development and synaptic activity; it sustains neurite outgrowth, neuronal migration, cortical lamination, and survival [1,2,3,4,5,6,7,8,9]. We identified a 125-residue truncated fragment of p35 called CIP that effectively and inhibited Cdk5-p25 activity and Tau hyperphosphorylation induced by A␤ peptides in vitro, in HEK293 cells, and in neuronal cells.

Results

Conclusion