The Presenilin-2 Loop Peptide Perturbs Intracellular Ca2+ Homeostasis and Accelerates Apoptosis

Peihui Lin,Christina Levchook,Na Li,J. Kevin Foskett,David Danielpour,King-Ho Cheung,Christopher Ferrante,Jianjie Ma,Gabrielle L. Boulianne,Chuanxi Cai,Zui Pan

doi:10.1074/jbc.m512026200

Abstract

In cells undergoing apoptosis, a 22-amino-acid presenilin-2-loop peptide (PS2-LP, amino acids 308-329 in presenilin-2) is generated through cleavage of the carboxyl-terminal fragment of presenilin-2 by caspase-3. The impact of PS2-LP on the progression of apoptosis, however, is not known. Here we show that PS2-LP is a potent inducer of the mitochondrial-dependent cell death pathway when transduced as a fusion protein with HIV-TAT. Biochemical and functional studies demonstrate that TAT-PS2-LP can interact with the inositol 1,4,5-trisphosphate receptor and activate Ca(2+) release from the endoplasmic reticulum. These results indicate that PS2-LP-mediated alteration of intracellular Ca(2+) homeostasis may be linked to the acceleration of apoptosis. Therefore, targeting the function of PS2-LP could provide a useful therapeutic tool for the treatment of cancer and degenerative diseases.

Highlights

A characteristic feature of PS1 and PS2 is their proteolysis by an endogenous presenilinase, generating amino-terminal (NTF) and carboxyl-terminal fragments (CTF) within cells [6, 7]
Expression and Purification of TAT Fusion Proteins and Delivery of TAT-presenilin-2-loop peptide (PS2-LP) into NRP-154 Cells—Previous studies have shown that PS2-LP could be generated via double cleavage of PS-2 by presenilinase and caspase-3 (Fig. 1A) [6, 7, 11]
We have used the TAT protein-penetrating transduction system to investigate the possible involvement of PS2-LP in cell apoptosis and [Ca2ϩ]i homeostasis

Summary

Introduction

A characteristic feature of PS1 and PS2 is their proteolysis by an endogenous presenilinase, generating amino-terminal (NTF) and carboxyl-terminal fragments (CTF) within cells [6, 7]. Expression and Purification of TAT Fusion Proteins and Delivery of TAT-PS2-LP into NRP-154 Cells—Previous studies have shown that PS2-LP could be generated via double cleavage of PS-2 by presenilinase and caspase-3 (Fig. 1A) [6, 7, 11]. Green fluorescent cells could be observed following a 30-min incubation with 5 ␮M TAT-PS2-LP, revealing the effective membrane penetrating capability of the TAT-PS2-LP peptide into NRP-154 cells.

Results

Conclusion