Recent studies have reported that many proteases, besides the canonical α-, β-, and γ-secretases, cleave the amyloid precursor protein (APP) and modulate β-amyloid (Aβ) peptide production. Moreover, specific APP isoforms contain Kunitz protease-inhibitory domains, which regulate the proteolytic activity of serine proteases. This prompted us to investigate the role of matriptase, a member of the type II transmembrane serine protease family, in APP processing. Using quantitative RT-PCR, we detected matriptase mRNA in several regions of the human brain with an enrichment in neurons. RNA sequencing data of human dorsolateral prefrontal cortex revealed relatively high levels of matriptase RNA in young individuals, whereas lower levels were detected in older individuals. We further demonstrate that matriptase and APP directly interact with each other and that matriptase cleaves APP at a specific arginine residue (Arg-102) both and in cells. Site-directed (Arg-to-Ala) mutagenesis of this cleavage site abolished matriptase-mediated APP processing. Moreover, we observed that a soluble, shed matriptase form cleaves endogenous APP in SH-SY5Y cells and that this cleavage significantly reduces APP processing to Aβ40. In summary, this study identifies matriptase as an APP-cleaving enzyme, an activity that could have important consequences for the abundance of Aβ and in Alzheimer's disease pathology.
A new approach to treating Duchenne muscular dystrophy was investigated by using the ester or amide covalent association of arginine [nitric oxide (NO) pathway] and butyrate [histone deacetylase (HDAC) inhibition] in mdx mice and patient myotubes. Two prodrugs were synthesized, and the beneficial effects on dystrophic phenotype were studied. Nerve excitability abnormalities detected in saline-treated mice were almost totally rescued in animals treated at low doses (50-100 mg/kg/d). Force and fatigue resistance were improved ≈60% and 3.5-fold, respectively, and the percentage of necrosis in heart sections was reduced ≈90% in the treated mice. A decrease of >50% in serum creatine kinase indicated an overall improvement in the muscles. Restoration of membrane integrity was studied directly by measuring the reduction (≈74%) of Evans blue incorporation in the limb muscles of the treated animals, the increase in utrophin level, and the normalization of lipid composition of the heart. In cultures of human myotubes (primary cells and cell line), both prodrugs and HDAC inhibitors increased by 2- to 4-fold the utrophin level, which was correctly localized at the membrane. β-Dystroglycan and embryonic myosin protein levels were also increased. Finally, a 50% reduction in the number of spontaneous Ca(2+) spikes was observed after treatment with NO synthase substrate and HDAC inhibitors. Overall, the beneficial effects were obtained with doses 10 (in vivo) and 5 (in vitro) times lower than those of the salt formulation. Altogether, these data constitute proof of principle of the beneficial effects of low doses of arginine butyrate derivatives on muscular dystrophy, enhancing the NO pathway and inhibiting HDAC.
The amyloid beta peptide (Aβ) is derived from the amyloid precursor protein (APP) by secretase processing. APP is also cleaved by numerous other proteases, such as the type II transmembrane serine protease matriptase, with consequences on the production of Aβ. Because the APP homolog protein amyloid-like protein 1 (APLP1) shares similarities with APP, we sought to determine if matriptase also plays a role in its processing. Here, we demonstrate that matriptase directly interacts with APLP1 and that APLP1 is cleaved in cellulo by matriptase in its E1 ectodomains at arginine 124. Replacing Arg124 with Ala abolished APLP1 processing by matriptase. Using a bioluminescence resonance energy transfer (BRET) assay we found that matriptase reduces APLP1 homodimeric interactions. This study identifies matriptase as the first protease cleaving APLP1 in its dimerization domain, potentially altering the multiple functions associated with dimer formation. Alzheimer's disease (AD) is a neurodegenerative disease characterized by a progressive and accelerated loss of neurons, leading to cognitive disorders and is currently the most common dementia 1. Accumulation of extracellular amyloid beta (Aβ) whether in the form of plaques, oligomers or soluble monomers is a fundamental hallmark of AD 2,3. In the pathogenic amyloidogenic pathway, successive APP cleavages by βand γ-secretase results in the production of Aβ 4. Recent treatment strategies targeting elements of the amyloidogenic pathway have failed to slow the progression of symptoms. Therefore, a better understanding of the mechanisms involved in AD is needed and several teams have focused on the physiological role and biosynthesis/processing of APP family members. Amyloid-like protein 1 (APLP1) is part of the same family and is homologous to APP 5. According to the Human Protein Atlas 6,7 , APLP1 is enriched in the human brain while APP is ubiquitously expressed, consistent with data obtained in mice 8. APP and APLP1 are type I transmembrane proteins sharing conserved luminal E1 and E2 domains 5. The E1 domain, rich in cysteines, is comprised of two subdomains, a growth factor-like subdomain (GFLD) that binds heparin and that stimulates neurite growth, as well as a CuBD subdomain that binds Cu and Zn ions 9. The E2 domain forms an antiparallel dimer and binds heparin in its dimeric form 10. Finally, the C-terminal domains of these proteins contain a YENPTY motif that serves as an endocytosis signal 11. Although both proteins can be cleaved by secretases, the Aβ sequence is only found in APP 12,13. APP and APLP1 are both involved in neuronal differentiation, synaptogenesis, neurite growth, and synaptic plasticity 14-16. APP and APLP1 are known to form homo-and heterodimers 17 , which are in part dependent on the conserved E1 domain 18. These dimeric interactions occur at the plasma membrane on a single cell (cis interaction) but also occur between transmembrane proteins of adjacent cells (trans interaction) 19-21. APP/APLP1 interactions promote cell adhesion in a homo-and heter...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.