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31 Publications visible to you, out of a total of 31

Abstract (Expand)

The metalloprotease ADAM10 is a drug target in Alzheimer's disease, where it cleaves the amyloid precursor protein (APP) and lowers amyloid-beta. Yet, ADAM10 has additional substrates, which may cause mechanism-based side effects upon therapeutic ADAM10 activation. However, they may also serve-in addition to APP-as biomarkers to monitor ADAM10 activity in patients and to develop APP-selective ADAM10 activators. Our study demonstrates that one such substrate is the neuronal cell adhesion protein NrCAM ADAM10 controlled NrCAM surface levels and regulated neurite outgrowth in vitro in an NrCAM-dependent manner. However, ADAM10 cleavage of NrCAM, in contrast to APP, was not stimulated by the ADAM10 activator acitretin, suggesting that substrate-selective ADAM10 activation may be feasible. Indeed, a whole proteome analysis of human CSF from a phase II clinical trial showed that acitretin, which enhanced APP cleavage by ADAM10, spared most other ADAM10 substrates in brain, including NrCAM Taken together, this study demonstrates an NrCAM-dependent function for ADAM10 in neurite outgrowth and reveals that a substrate-selective, therapeutic ADAM10 activation is possible and may be monitored with NrCAM.

Authors: T. Brummer, S. A. Muller, F. Pan-Montojo, F. Yoshida, A. Fellgiebel, T. Tomita, K. Endres, S. F. Lichtenthaler

Date Published: 6th Mar 2019

Publication Type: Journal

Abstract (Expand)

Members of the GxGD-type intramembrane aspartyl proteases have emerged as key players not only in fundamental cellular processes such as B-cell development or protein glycosylation, but also in development of pathologies, such as Alzheimer's disease or hepatitis virus infections. However, one member of this protease family, signal peptide peptidase-like 2c (SPPL2c), remains orphan and its capability of proteolysis as well as its physiological function is still enigmatic. Here, we demonstrate that SPPL2c is catalytically active and identify a variety of SPPL2c candidate substrates using proteomics. The majority of the SPPL2c candidate substrates cluster to the biological process of vesicular trafficking. Analysis of selected SNARE proteins reveals proteolytic processing by SPPL2c that impairs vesicular transport and causes retention of cargo proteins in the endoplasmic reticulum. As a consequence, the integrity of subcellular compartments, in particular the Golgi, is disturbed. Together with a strikingly high physiological SPPL2c expression in testis, our data suggest involvement of SPPL2c in acrosome formation during spermatogenesis.

Authors: A. A. Papadopoulou, S. A. Muller, T. Mentrup, M. D. Shmueli, J. Niemeyer, M. Haug-Kroper, J. von Blume, A. Mayerhofer, R. Feederle, B. Schroder, S. F. Lichtenthaler, R. Fluhrer

Date Published: 9th Feb 2019

Publication Type: Journal

Abstract (Expand)

Signal peptide peptidase (SPP) and the four homologous SPP-like (SPPL) proteases constitute a family of intramembrane aspartyl proteases with selectivity for type II-oriented transmembrane segments. Here, we analyse the physiological function of the orphan protease SPPL2c, previously considered to represent a non-expressed pseudogene. We demonstrate proteolytic activity of SPPL2c towards selected tail-anchored proteins. Despite shared ER localisation, SPPL2c and SPP exhibit distinct, though partially overlapping substrate spectra and inhibitory profiles, and are organised in different high molecular weight complexes. Interestingly, SPPL2c is specifically expressed in murine and human testis where it is primarily localised in spermatids. In mice, SPPL2c deficiency leads to a partial loss of elongated spermatids and reduced motility of mature spermatozoa, but preserved fertility. However, matings of male and female SPPL2c(-/-) mice exhibit reduced litter sizes. Using proteomics we identify the sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA2)-regulating protein phospholamban (PLN) as a physiological SPPL2c substrate. Accumulation of PLN correlates with a decrease in intracellular Ca(2+) levels in elongated spermatids that likely contribute to the compromised male germ cell differentiation and function of SPPL2c(-/-) mice.

Authors: J. Niemeyer, T. Mentrup, R. Heidasch, S. A. Muller, U. Biswas, R. Meyer, A. A. Papadopoulou, V. Dederer, M. Haug-Kroper, V. Adamski, R. Lullmann-Rauch, M. Bergmann, A. Mayerhofer, P. Saftig, G. Wennemuth, R. Jessberger, R. Fluhrer, S. F. Lichtenthaler, M. K. Lemberg, B. Schroder

Date Published: 9th Feb 2019

Publication Type: Journal

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