Positive- and negative-regulation of Ca2+ entry through ACh receptor channels by phosphorylation

During development of mammalian neuromuscular junctions, the expression of ACh receptors (AChRs) switches from an embryonic form to an adult form, which provides a higher Ca2+ permeable channel. The lack of this switch can prevent normal development of neuromuscular junctions. In non-mammalian species, however, the switch appears not to occur. The results of the present study show that Ca2+ entry through non-mammalian AChR channels was controlled by differential phosphorylation rather than a subunit switch. This finding provides support for the hypothesis that localized Ca2+ influx through AChR channels has a critical role in the formation and maintenance of neuromuscular junctions.