Deletion or inhibition of prolyl oligopeptidase blocks lithium‐induced phosphorylation of GSK3b and Akt by activation of protein phosphatase 2A

Abstract

Alterations in prolyl oligopeptidase (PREP) activity have been connected, for example, with bipolar and major depressive disorder, and several studies have reported that lack or inhibition of PREP blocks the effects of lithium on inositol 1,4,5-triphosphate (IP 3 ) levels. However, the impact of PREP modulation on other intracellular targets of lithium, such as glycogen synthase kinase 3 beta (GSK3b) or protein kinase B (Akt), has not been studied. We recently found that PREP regulates protein phosphatase 2A (PP2A), and because GSK3b and Akt are PP2A substrates, we studied if PREP-related lithium insensitivity is dependent on PP2A. To assess this, HEK-293 and SH-SY5Y cells with PREP deletion or PREP inhibition (KYP-2047) were exposed to lithium, and thereafter, the phosphorylation levels of GSK3b and Akt were measured by Western blot. As expected, PREP deletion and inhibition blocked the lithiuminduced phosphorylation on GSK3b and Akt in both cell lines. When lithium exposure was combined with okadaic acid, a PP2A inhibitor, KYP-2047 did not have effect on lithium-induced GSK3b and Akt phosphorylation. Therefore, we conclude that PREP deletion or inhibition blocks the intracellular effects of lithium on GSK3b and Akt via PP2A activation.

Delivery of Active AKT1 to Human Cells

“…AKT1 is also highly expressed in many human tissues, including the kidney [ 42 ], making HEK 293T cells an appropriate model system to study AKT1 signaling. Indeed, some of the initial characterizations of AKT1 activity [ 43 ] as well as more recent studies to screen AKT1 inhibitors [ 44 ] and to define new roles for AKT1 in diverse cellular processes including RNA metabolism [ 45 , 46 ], miRNA regulation [ 31 ], and non-sense mediated decay [ 47 ] each relied on HEK 293 cells as an appropriate cell line to investigate AKT1 biology.…”

The effects of the tumor suppressor gene PTEN on the proliferation and apoptosis of breast cancer cells via AKT phosphorylation

“…Breast cancer is a common malignant tumor in Chinese women, and its mechanism of action has attracted increasing attention. It has been found that PTEN is located at the 10q23 locus of the human chromosome, which is 200 bp long and contains 8 introns and 9 exons ( 16 ). The biological functions of PTEN include inducing cell cycle arrest and apoptosis, inhibiting local cell adhesion, migration and angiogenesis, and playing an important role in the occurrence and development of many tumors.…”