Cerebral expression of the alpha sub(2)-subunit of soluble guanylyl cyclase is linked to cerebral maturation and sensory pathway refinement during postnatal development

Soluble guanylyl cylase (sGC) has been identified for being a receptor for the gaseous transmitters nitric oxide and cabon monoxide. Currently four subunits alpha sub(1), alpha sub(2), beta sub(1), and beta sub(2) have been characterized. Heterodimers of alpha and beta -subunits as well as homodimers of the beta sub(2)-subunit are known to constitute functional sGC which use GTP to form cGMP a potent signal molecule in a multitude of second messenger cascades. Since NO-cGMP signaling plays a pivotal role in neuronal development we analyzed the maturational expression pattern of the newly characterized alpha sub(2)-subunit of sGC within the brain of Wistar rats by means of RNase protection assay and immunohistochemistry. alpha sub(2)-subunit mRNA as well as immunoreactive alpha sub(2)-protein increased during postnatal cerebral development. Topographical analysis revealed a selective high expression of the alpha sub(2)-subunit in the choroid plexus and within developing sensory systems involving the olfactory and somatosensory system of the forebrain as well as parts of the auditory and visual system within the hindbrain. In cultured cortical neurons the alpha sub(2)-subunit was localized to the cell membrane, especially along neuronal processes. During the first 11 days of postnatal development several cerebral regions showed a distinct expression of the alpha sub(2)-subunit which was not paralleled by the alpha sub(1)/ beta sub(1)-subunits especially within the developing thalamo-cortical circuitries of the somatosensory system. However, at later developmental stages all three subunits became more homogenously distributed among most cerebral regions, indicating that functional alpha sub(1)/ beta sub(1) and alpha sub(2/) beta sub(1) heterodimers of sGC could be formed. Our findings indicate that the alpha sub(2)-subunit is an essential developmentally regulated constituent of cerebral sensory systems during maturation. In addition the alpha sub(2)-subunit may serve other functions than forming a functional heterodimer of sGC during the early phases of sensory pathway refinement.