Search results for "precursor"

Effects of sulindac sulfide on the membrane architecture and the activity of gamma-secretase.

2007

gamma-Secretase is a membrane-embedded multi-protein complex that catalyzes the final cut of the Alzheimer's disease-related amyloid precursor protein (APP) to amyloid-beta peptides of variable length (37-43 amino acids) via an unusual intramembrane cleavage. Recent findings propose that some commonly used non-steroidal anti-inflammatory drugs (NSAIDs) have the ability to modulate specifically gamma-secretase activity without inhibiting the enzyme as a whole. These drugs may shift the processing of APP from the longer amyloid-beta 42 peptide towards shorter, less fibrillogenic and less toxic amyloid-beta species. We hypothesize that gamma-secretase activity, as an enzyme that is strictly as…

Analyzing the protease web in skin: meprin metalloproteases are activated specifically by KLK4, 5 and 8 vice versa leading to processing of proKLK7 t…

2010

Abstract The metalloproteases meprin α and β are expressed in several tissues, leukocytes, and cancer cells. In skin, meprins are located in separate layers of human epidermis indicating distinct physiological functions, supported by effects on cultured keratinocytes. Meprin β induces a dramatic change in cell morphology and a significant reduction in cell number, whereas in vitro evidence suggests a role for meprin α in basal keratinocyte proliferation. Meprins are secreted as zymogens that are activated by tryptic proteolytical processing. Here, we identify human kallikrein-related peptidases (KLKs) 4, 5, and 8 to be specific activators of meprins. KLK5 is capable of activating both metal…

SANS (USH1G) regulates pre-mRNA splicing by mediating the intra-nuclear transfer of tri-snRNP complexes

2021

Abstract Splicing is catalyzed by the spliceosome, a compositionally dynamic complex assembled stepwise on pre-mRNA. We reveal links between splicing machinery components and the intrinsically disordered ciliopathy protein SANS. Pathogenic mutations in SANS/USH1G lead to Usher syndrome—the most common cause of deaf-blindness. Previously, SANS was shown to function only in the cytosol and primary cilia. Here, we have uncovered molecular links between SANS and pre-mRNA splicing catalyzed by the spliceosome in the nucleus. We show that SANS is found in Cajal bodies and nuclear speckles, where it interacts with components of spliceosomal sub-complexes such as SF3B1 and the large splicing cofact…

The Metalloprotease Meprin β Generates Amino Terminal-truncated Amyloid β Peptide Species

2012

The amyloid β (Aβ) peptide, which is abundantly found in the brains of patients suffering from Alzheimer disease, is central in the pathogenesis of this disease. Therefore, to understand the processing of the amyloid precursor protein (APP) is of critical importance. Recently, we demonstrated that the metalloprotease meprin β cleaves APP and liberates soluble N-terminal APP (N-APP) fragments. In this work, we present evidence that meprin β can also process APP in a manner reminiscent of β-secretase. We identified cleavage sites of meprin β in the amyloid β sequence of the wild type and Swedish mutant of APP at positions p1 and p2, thereby generating Aβ variants starting at the first or seco…

LC–MS Based Cleavage Site Profiling of the Proteases ADAM10 and ADAM17 Using Proteome-Derived Peptide Libraries

2014

A Disintegrin and Metalloproteinase 10 (ADAM10) and ADAM17 catalyze ectodomain shedding of a number of cell surface proteins important for embryonic development and tissue homeostasis. Changes in the expression levels or dysregulated proteolytic activity of ADAM10 and ADAM17 have been shown to play important roles in multiple diseases such as inflammation, cancer, and neurodegenerative disorders. Despite the well documented substrate repertoire of ADAM10 and ADAM17, little is known about their cleavage site specificity. We optimized Q-PICS (Quantitative Proteomics for the Identification of Cleavage Sites) to elucidate the cleavage site specificity of recombinant murine ADAM10 and ADAM17. Tw…

The substrate degradome of meprin metalloproteases reveals an unexpected proteolytic link between meprin β and ADAM10

2012

The in vivo roles of meprin metalloproteases in pathophysiological conditions remain elusive. Substrates define protease roles. Therefore, to identify natural substrates for human meprin α and β we employed TAILS (terminal amine isotopic labeling of substrates), a proteomics approach that enriches for N-terminal peptides of proteins and cleavage fragments. Of the 151 new extracellular substrates we identified, it was notable that ADAM10 (a disintegrin and metalloprotease domain-containing protein 10)—the constitutive α-secretase—is activated by meprin β through cleavage of the propeptide. To validate this cleavage event, we expressed recombinant proADAM10 and after preincubation with meprin…

Discovery of γ-secretase modulators with a novel activity profile by text-based virtual screening.

2012

We present an integrated approach to identify and optimize a novel class of γ-secretase modulators (GSMs) with a unique pharmacological profile. Our strategy included (i) virtual screening through application of a recently developed protocol (PhAST), (ii) synthetic chemistry to discover structure–activity relationships, and (iii) detailed in vitro pharmacological characterization. GSMs are promising agents for treatment or prevention of Alzheimer’s disease. They modulate the γ-secretase product spectrum (i.e., amyloid-β (Aβ) peptides of different length) and induce a shift from toxic Aβ42 to shorter Aβ species such as Aβ38 with no or minimal effect on the overall rate of γ-secretase cleavag…

Alcadein cleavages by amyloid beta-precursor protein (APP) alpha- and gamma-secretases generate small peptides, p3-Alcs, indicating Alzheimer disease…

2009

Alcadeins (Alcs) constitute a family of neuronal type I membrane proteins, designated Alc(alpha), Alc(beta), and Alc(gamma). The Alcs express in neurons dominantly and largely colocalize with the Alzheimer amyloid precursor protein (APP) in the brain. Alcs and APP show an identical function as a cargo receptor of kinesin-1. Moreover, proteolytic processing of Alc proteins appears highly similar to that of APP. We found that APP alpha-secretases ADAM 10 and ADAM 17 primarily cleave Alc proteins and trigger the subsequent secondary intramembranous cleavage of Alc C-terminal fragments by a presenilin-dependent gamma-secretase complex, thereby generating "APP p3-like" and non-aggregative Alc pe…

Anything but Ordinary - Emerging Splicing Mechanisms in Eukaryotic Gene Regulation.

2021

Splicing of precursor mRNAs (pre-mRNA) is an important step during eukaryotic gene expression. The identification of the actual splice sites and the proper removal of introns are essential for the production of the desired mRNA isoforms and their encoded proteins. While the basic mechanisms of splicing regulation are well understood, recent work has uncovered a growing number of noncanonical splicing mechanisms that play key roles in the regulation of gene expression. In this review, we summarize the current principles of splicing regulation, including the impact of cis and trans regulatory elements, as well as the influence of chromatin structure, transcription, and RNA modifications. We f…

2014

In the pathogenesis of Alzheimer’s disease (AD) the homeostasis of amyloid precursor protein (APP) processing in the brain is impaired. The expression of the competing proteases ADAM10 (a disintegrin and metalloproteinase 10) and BACE-1 (beta site APP cleaving enzyme 1) is shifted in favor of the A-beta generating enzyme BACE-1. Acitretin–a synthetic retinoid–e.g., has been shown to increase ADAM10 gene expression, resulting in a decreased level of A-beta peptides within the brain of AD model mice and thus is of possible value for AD therapy. A striking challenge in evaluating novel therapeutically applicable drugs is the analysis of their potential to overcome the blood-brain barrier (BBB)…