Role of γ-Secretase Inhibitors for the Treatment of Diverse Disease Conditions through Inhibition of Notch Signaling Pathway

γ-Secretase is an intramembrane protease sub-assembly which that sunders transmembrane proteins. They are involved in intramembrane proteolysis and also contribute to the regeneration of transmembrane protein. The amyloid precursor protein (APP) is a typical γ-secretase substrate. These proteins are cleaved to produce 36-43 amyloid-beta (Aβ) amino acid peptides. Abnormal folding of these protein fragments leads to amyloid plaques; , frequently encountered in Alzheimer's disease. Some Type I class of integral membrane proteins are processed under the influence of γ-secretase, such as receptor tyrosine-protein kinase erbB4 and CD44 glycoprotein. γ-Secretase is being explored in a number of diseases as a clinical goal. Both γ-secretase inhibitors (GSIs) and γ-secretase modulators (GSMs) are being evaluated for this purpose. A large amount of γ-secretase inhibitors (GSIs) from peptide to non-peptide have been disclosed, offering several lead compounds for the design and optimization of γ-secretase targets, but most GSIs lacks sufficient potency, low penetration in the brain, and low selectiveness. γ-Secretase inhibitors are obliquely a regulator of a γ-secretase substrate Notch, and valuable in the understanding of the development of β-amyloid peptide (Aβ). These γ-secretase inhibitors block the Notch signaling pathway in autoimmune and lymphoproliferative disorders like autoimmune lymphoproliferative syndrome (ALPS) and systemic lupus erythematosus (SLE), and perhaps even in cancerous cell proliferation, angiogenesis, and cellular differentiation of human-induced pluripotent stem cells (hiPSC). The current review portrays the mechanism, regulation, and inhibition of γ-secretase in the management of a wide assortment of diseases.

Mutation of the Kunitz-type proteinase inhibitor domain in the amyloid β-protein precursor abolishes its anti-thrombotic properties in vivo

INTRODUCTION

Kunitz proteinase inhibitor (KPI) domain-containing forms of the amyloid β-protein precursor (AβPP) inhibit cerebral thrombosis. KPI domain-lacking forms of AβPP are abundant in brain. Regions of AβPP other than the KPI domain may also be involved with regulating cerebral thrombosis. To determine the contribution of the KPI domain to the overall function of AβPP in regulating cerebral thrombosis we generated a reactive center mutant that was devoid of anti-thrombotic activity and studied its anti-thrombotic function in vitro and in vivo.

METHODS

To determine the extent of KPI function of AβPP in regulating cerebral thrombosis we generated a recombinant reactive center KPI^R13I mutant devoid of anti-thrombotic activity. The anti-proteolytic and anti-coagulant properties of wild-type and R13I mutant KPI were investigated in vitro. Cerebral thrombosis of wild-type, AβPP knock out and AβPP/KPI^R13I mutant mice was evaluated in experimental models of carotid artery thrombosis and intracerebral hemorrhage.

RESULTS

Recombinant mutant KPI^R13I domain was ineffective in the inhibition of pro-thrombotic proteinases and did not inhibit the clotting of plasma in vitro. AβPP/KPI^R13I mutant mice were similarly deficient as AβPP knock out mice in regulating cerebral thrombosis in experimental models of carotid artery thrombosis and intracerebral hemorrhage.

CONCLUSIONS

We demonstrate that the anti-thrombotic function of AβPP primarily resides in the KPI activity of the protein.

Stabilization of intracellular trafficking and metabolism of amyloid β-protein precursor and Alcadein β by apolipoprotein E

Intracellular metabolism of amyloid β-protein precursor (APP) is important for the pathogenesis of Alzheimer's disease (AD). Alcadeins (Alcα, Alcβ, and Alcγ) are neural membrane proteins similar to APP in their localization, metabolism, and cellular function. Isoform ε4 of apolipoprotein E (ApoE) is a major risk factor for AD. We found that ApoE expression attenuated intracellular trafficking of APP and Alcβ, resulting in metabolic stabilization of both proteins. By contrast, Alcα intracellular proteolysis was facilitated by ApoE expression, which was not due to an increase in the primary cleavage of Alcα. This difference may result from binding of ApoE to membrane proteins.