title: Cu-Zn superoxide dismutase activates muscarinic acetylcholine M1 receptor pathway in neuroblastoma cells.
abstract: Muscarinic receptors (mAChRs) control several neuronal functions and are widely expressed in the central nervous system (CNS): M1 subtype represents the predominant mAChR in the CNS. Previously, we showed that antioxidant enzyme Cu-Zn superoxide dismutase (SOD1) is secreted by many cellular lines and specifically interacts with cell surface membrane of human neuroblastoma SK-N-BE cells thus activating phospholipase C (PLC) transduction pathway and increasing intracellular calcium concentration ([Ca(2+)](i)). In addition, we demonstrated that a small amount of SOD1 is contained in large core dense vesicles and that it is secreted in response to depolarization induced by elevated extracellular K(+) concentration. In the present study, we investigated the involvement of muscarinic M1 receptors in SOD1-induced activation of PLC transduction pathway. We showed that, in SK-N-BE cells, SOD1 was able to activate muscarinic M1 receptor producing a phosphorylation of ERK 1/2 and Akt in dose- and time-dependent manner. Interestingly, in the presence of the M1 antagonist pirenzepine, ERK 1/2 and Akt phosphorylation induced by SOD1 was remarkably prevented. This effect was mimicked by knocking-down M1 receptor using two sequences of RNA silencing (siRNA). At functional level, siRNAs against M1 receptor were able to prevent the increase in [Ca(2+)](i) induced by SOD1. The same inhibitory effect on [Ca(2+)](i) changes was produced by the M1 antagonist pirenzepine. Collectively, the results of this study demonstrated that SOD1 could activate a transductional pathway through the involvement of M1 muscarinic receptor.
authors.affiliation: Dipartimento di Neuroscienze, Unità di Fisiologia Umana, Università degli Studi di Napoli Federico II, Napoli, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Damiano
authors.forename: Tiziana
authors.initials: T
authors.lastname: Petrozziello
authors.forename: Valentina
authors.initials: V
authors.lastname: Ucci
authors.forename: Stefano
authors.initials: S
authors.lastname: Amente
authors.forename: Mariarosaria
authors.initials: M
authors.lastname: Santillo
authors.forename: Paolo
authors.initials: P
authors.lastname: Mondola
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism*; D034622:RNA Interference; D043643:Receptor, Muscarinic M1 / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013482:Superoxide Dismutase / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D043643:Receptor, Muscarinic M1; D013482:Superoxide Dismutase; D010738:Type C Phospholipases