In this work we examined the possible interactions between the neuregulin 1 (NRG1) -ErbB4 system and the NMDA-type glutamate receptor (NMDAR) in the migratory process of ST14A immortalized neural progenitors. RT-PCR studies showed that both wild-type ST14A cells (non-expressing ErbB4), as well as ErbB4-transfected clones express a restricted number of NMDAR subunits: NR1, NR2C, NR2D and NR3B, suggesting a channel conformation with low Mg2+-sensitivity and low Ca2+-permeability, and generating small, long-lasting responses. Migration assays showed no NMDA effect on ErbB4-transfected ST14A cells. However, when NMDA was added to NRG1, there was a 5 to 8 fold increase in NRG1-induced migration. Since the NMDAR is a Ca2+-permeable channel, we asked whether the synergism with the NRG1/ErbB4 system could be Ca2+-dependent. Migration assays carried out in the presence of the intracellular Ca2+ chelator BAPTA-AM showed a highly significant reduction in NMDA+NRG1 stimulated migration, shifting the number of migrated cells approximately to the level of NRG1 treatment alone. In calcium-imaging experiments we found that NRG1 stimulation of ErbB4-transfected ST14A cells induced a strong increase in [Ca2+]i. This increase was significantly lower when NRG1 stimulation was repeated in Ca2+–free medium, suggesting that calcium rises are due to both extracellular Ca2+ influx and release from internal stores. After termination of NRG1 stimulation in Ca2+–free medium and subsequent re-addition of extracellular Ca2+, the level of [Ca2+]i further increased, suggesting the involvement of a store operated mechanism (SOCE). NMDA stimulation led to very small increases in [Ca2+]i, consistent with a lower expression of NMDARs compared to ErbB4 receptors in transfected ST14A clones. In summary, this experimental work suggests an interaction between NMDA receptors and the NRG1-ErbB4 system in neural precursor migration. This interaction is calcium-dependent and may rely on multiple mechanisms.
NRG1/ErbB4-induced migration in ST14A striatal progenitors is modulated by NMDA receptor through calcium-dependent mechanisms.
GAMBAROTTA, Giovanna;PREGNO, GIULIA;ZAMBURLIN, Pollyanna;FARCITO, SILVIA;PERROTEAU, Isabelle;LOVISOLO, Davide;BOVOLIN, Patrizia
2010-01-01
Abstract
In this work we examined the possible interactions between the neuregulin 1 (NRG1) -ErbB4 system and the NMDA-type glutamate receptor (NMDAR) in the migratory process of ST14A immortalized neural progenitors. RT-PCR studies showed that both wild-type ST14A cells (non-expressing ErbB4), as well as ErbB4-transfected clones express a restricted number of NMDAR subunits: NR1, NR2C, NR2D and NR3B, suggesting a channel conformation with low Mg2+-sensitivity and low Ca2+-permeability, and generating small, long-lasting responses. Migration assays showed no NMDA effect on ErbB4-transfected ST14A cells. However, when NMDA was added to NRG1, there was a 5 to 8 fold increase in NRG1-induced migration. Since the NMDAR is a Ca2+-permeable channel, we asked whether the synergism with the NRG1/ErbB4 system could be Ca2+-dependent. Migration assays carried out in the presence of the intracellular Ca2+ chelator BAPTA-AM showed a highly significant reduction in NMDA+NRG1 stimulated migration, shifting the number of migrated cells approximately to the level of NRG1 treatment alone. In calcium-imaging experiments we found that NRG1 stimulation of ErbB4-transfected ST14A cells induced a strong increase in [Ca2+]i. This increase was significantly lower when NRG1 stimulation was repeated in Ca2+–free medium, suggesting that calcium rises are due to both extracellular Ca2+ influx and release from internal stores. After termination of NRG1 stimulation in Ca2+–free medium and subsequent re-addition of extracellular Ca2+, the level of [Ca2+]i further increased, suggesting the involvement of a store operated mechanism (SOCE). NMDA stimulation led to very small increases in [Ca2+]i, consistent with a lower expression of NMDARs compared to ErbB4 receptors in transfected ST14A clones. In summary, this experimental work suggests an interaction between NMDA receptors and the NRG1-ErbB4 system in neural precursor migration. This interaction is calcium-dependent and may rely on multiple mechanisms.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
