Differential expression of NO-sensitive guanylyl cyclase subunits during the development of rat cerebellar granule cells: regulation via N-methyl-D-aspartate receptors

Abstract

In primary cultures of rat cerebellar granule cells with a functional network of glutamatergic neurons, the expression pattern of the different subunits of nitric-oxide (NO)-sensitive guanylyl cyclase changes during cell differentiation. These cells express the α1,α 2 and β1 subunits of NO-sensitive guanylyl cyclase and synthesize cyclic guanosine monophosphate (cGMP) in response to exogenous or endogenous nitric oxide. In this study, we determined the protein content of the α1 and β1 subunits and quantified α1, α2 and β1mRNA by reverse transcription coupled to a polymerase chain reaction (RT-PCR). Expression of the β1 subunit increased with the degree of cell differentiation, although most marked changes occurred at the α subunit level. In cells freshly isolated from rat pups on postnatal day 7 (P7) the most abundant α subunit was α1, whileα 2 appeared as the predominant subunit of this type in cultured cells. N-methyl-D-aspartate (NMDA) receptor stimulation in 7- or 14-day-cultured cells led to the upregulation of guanylyl cyclase subunit mRNAs; α2 mRNA levels undergoing most significant change. This enhanced subunit expression was accompanied by an increase in the amount of cGMP synthesized in response to NO. Thus, it seems thatα 2 subunits are increasingly expressed as granule cells mature. The presence of this subunit in the guanylyl cyclase heterodimer facilitates its localization at synaptic membranes, where the enzyme acts as a sensor for NO formed by the postsynaptic protein 95 (PSD-95)-associated neuronal NO synthase.