The catalytic core of photoreceptor-specific @entity6708 -phosphodiesterase (PDE) consists of two subunits, @entity39446 , that are homologous and have similar domain organization but are encoded by different genes. We have examined the @entity39446 mRNA steady-state and protein levels as well as the biosynthesis rate of these proteins in developing and fully differentiated retinas. We have also determined the translational efficiency of PDE subunits and the role of their mRNA structures in regulating protein synthesis. In mature retinas, @entity39446 are represented by approximately 1.5 x 108 and 7.5 x 108 copies/microg retinal mRNA, respectively. The levels of these transcripts in developing photoreceptors (P10) are approximately 75% of those at P30. Quantification of protein concentration indicated that @entity39446 are equally expressed in developing and fully differentiated photoreceptors. Furthermore, the @entity25667 /PDEbeta ratios obtained throughout a 2-h pulsechase period revealed a similar turnover rate for both subunits. The observed discordance between the mRNA and protein levels of @entity39446 suggested post-transcriptional regulation of their expression. We found that @entity25667 mRNA is translated more efficiently than either of the two PDEbeta transcripts expressed in retina. Therefore, the lower level of @entity25667 mRNA is compensated by its more efficient translation to achieve equimolar expression with PDEbeta. We also analyzed the effect of @entity39446 mRNA 5'- and 3'-untranslated regions as well as that of their coding regions on protein synthesis. We determined that the PDE-coding regions play a critical role in the differential translation of these subunits.

Differential expression of rod photoreceptor XXXX -phosphodiesterase alpha and beta subunits: mRNA and protein levels.

@entity6708 :: ('CHEBI:16356', 'Chemical') :: ['cGMP'] @entity39446 :: ('5158', 'Gene') :: ['PDEalpha and PDEbeta'] @entity25667 :: ('5145', 'Gene') :: ['PDEalpha']
@entity6708 :: (CHEBI:16356,Chemical) :: ['cGMP']
