ABSTRACT
Membrane-associated glycoprotein neural cell adhesion molecule (NCAM) and its polysialylated form (PSA-NCAM) play an important role in brain plasticity by regulating cell–cell interactions. Here, we demonstrate that the cytosolic serine protease prolyl endopeptidase (PREP) is able to regulate NCAM and PSA-NCAM. Using a SH-SY5Y neuroblastoma cell line with stable overexpression of PREP, we found a remarkable loss of PSA-NCAM, reduced levels of NCAM180 and NCAM140 protein species, and a significant increase in the NCAM immunoreactive band migrating at an apparent molecular weight of 120 kDa in PREP-overexpressing cells. Moreover, increased levels of NCAM fragments were found in the concentrated medium derived from PREP-overexpressing cells. PREP overexpression selectively induced an activation of matrix metalloproteinase-9 (MMP-9), which could be involved in the observed degradation of NCAM, as MMP-9 neutralization reduced the levels of NCAM fragments in cell culture medium. We propose that increased PREP levels promote epidermal growth factor receptor (EGFR) signaling, which in turn activates MMP-9. In conclusion, our findings provide evidence for newly-discovered roles for PREP in mechanisms regulating cellular plasticity through NCAM and PSA-NCAM.
Footnotes
Author contributions
K.J., A.W.: conception and design of the study, conduction of experimental work, statistical analysis and interpretation of the data, drafting and revision of the manuscript. K.P., L.K., A.A.-H., K.A., A.N.: participation in the experimental work, conduction of immunocytochemistry, western blot and qPCR. M.G.: generation PREP-overexpressing SH-SY5Y cell line. R.V.E., A.-M.L., S.R., M.M., A.Z.: approval of study design, interpretation of the data, critical revision of the article, approval of the final version of the manuscript.
Funding
This study was supported by the 7th Framework Programme of Health of the European Commission [project NEUROPRO, HEALTH-F2-2008-223077 to S.R., A.-M.L., A.Z.], Eesti Teadusfondi (Estonian Science Foundation) [grant number 8740 to K.J.] and Eesti Teadusagentuur (Estonian Research Council) [Institutional research funding grant IUT2-3 to A.Z.], the Deutsche Forschungsgemeinschaft (German Research Foundation) [grants MO 2249/2-1 and MO 2249/2-2 to M.M within the PP 1608], the Alzheimer Forschung Initiative [grant number 1186 to M.M.], Universiteit Antwerpen [special research fund grant FFB3551 to A-M.L. and R.V.E] and Sächsische Aufbaubank (SAB)/European Social Fund (ESF) [grant number SAB100154907 to S.R., M.M., A.Z. and A.W.].
