Several studies have indicated that mutations in the neuroligin family of synaptic adhesion proteins play an important role in the etiology of autistic spectral disorders. Genetic alterations in the neuroligins genes, including point mutations, exon deletions, and premature truncations have been identified in a small percentage of autistic patients indicating that impairments in synaptic function leads to deficits in brain development. Mutations affecting function, amounts, folding and trafficking of these proteins may contribute to an imbalance in the excitatory/inhibitory network, leading to impaired neuronal signaling, abnormal brain circuits and neurotransmission. The R451C mutation in NLGN3 has been shown to induce a local misfolding in the extracellular domain of the protein that results mostly retained in the ER. The mutation slows down protein processing in HEK-293 and trafficking in neurons with a small fraction still reaching the cell surface. Stronger association with specific chaperone proteins has been shown for the R451C mutant compared to the wild type protein indicating the activation of the ER quality control system in blocking the protein from exiting the ER. We have investigated whether the ER retained protein is activating the UPR response in a yeast model system, K. Lactis and in a mammalian cell system, HEK-293 cells. From our results it emerges that the NLGN3 R451C mutant protein is activating the expression of KAR2, the yeast BiP homologue, that is not observed with the wild type protein. In mammals cells, we studied the activation of distinct UPR signaling pathways by monitoring the splicing of XBP-1 and the activation of ER stress-responsive promoter elements, using a UPR element (UPRE)-luciferase construct in HEK-293 overexpressing either wild type or mutant proteins. From our preliminary data we can conclude that the NLGN3 R451C mutation associated to autism is retained in the ER and is activating an ER stress response.
Neuroligin 3 misfolding mutations and activation of the unfolded protein response / Uccelletti, Daniela; Ulbrich, Lisa; F., Lietta Favaloro; Zanni, Elena; DE JACO, Antonella. - STAMPA. - (2011). (Intervento presentato al convegno ABCD Congress 2011 tenutosi a Ravenna nel 8-10 Settembre).
Neuroligin 3 misfolding mutations and activation of the unfolded protein response
UCCELLETTI, Daniela;ULBRICH, Lisa;ZANNI, ELENA;DE JACO, Antonella
2011
Abstract
Several studies have indicated that mutations in the neuroligin family of synaptic adhesion proteins play an important role in the etiology of autistic spectral disorders. Genetic alterations in the neuroligins genes, including point mutations, exon deletions, and premature truncations have been identified in a small percentage of autistic patients indicating that impairments in synaptic function leads to deficits in brain development. Mutations affecting function, amounts, folding and trafficking of these proteins may contribute to an imbalance in the excitatory/inhibitory network, leading to impaired neuronal signaling, abnormal brain circuits and neurotransmission. The R451C mutation in NLGN3 has been shown to induce a local misfolding in the extracellular domain of the protein that results mostly retained in the ER. The mutation slows down protein processing in HEK-293 and trafficking in neurons with a small fraction still reaching the cell surface. Stronger association with specific chaperone proteins has been shown for the R451C mutant compared to the wild type protein indicating the activation of the ER quality control system in blocking the protein from exiting the ER. We have investigated whether the ER retained protein is activating the UPR response in a yeast model system, K. Lactis and in a mammalian cell system, HEK-293 cells. From our results it emerges that the NLGN3 R451C mutant protein is activating the expression of KAR2, the yeast BiP homologue, that is not observed with the wild type protein. In mammals cells, we studied the activation of distinct UPR signaling pathways by monitoring the splicing of XBP-1 and the activation of ER stress-responsive promoter elements, using a UPR element (UPRE)-luciferase construct in HEK-293 overexpressing either wild type or mutant proteins. From our preliminary data we can conclude that the NLGN3 R451C mutation associated to autism is retained in the ER and is activating an ER stress response.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
