Gene expression and protein localization of calmodulin‐dependent phosphodiesterase in adult rat retina

Abstract

Calcium calmodulin-dependent cyclic nucleotide phosphodiesterase (PDE1) was identified in crude extract and immunolabeled sections of rat retina. Both cAMP and cGMP PDE activities were stimulated by calcium-calmodulin (4.7-fold and 2.3-fold, respectively). To characterize PDE1 isoforms in retinal cells further, we used antibodies that specifically recognize PDE1 gene products. PDE1B antibody stained a band at molecular mass of 63 kDa whereas PDE1C antibody recognized two bands at 74- and 70-kDa molecular masses. Two PDE1A antibodies (against N-terminal and C-terminal peptides) detected a band at 79 kDa never described before. Immunohistochemical analysis showed a distribution of PDE1A in the outer retina with a bright fluorescence in the outer segments of photoreceptors. PDE1B is uniformly distributed across the retina. PDE1C is confined mainly to the inner retina, with a precise localization in the inner nuclear layer. Immunostaining with choline acetyltransferase antibody indicates localization in cholinergic amacrine cell. The present data provide evidence of expression of PDE1 isoforms in mammalian retina with a complementary distribution of PDE1A and PDE1C, suggesting different roles in retinal function.

Ca2+/calmodulin-activated phosphodiesterase 1A is highly expressed in rabbit cardiac sinoatrial nodal cells and regulates pacemaker function

“…Evidence in other cell types demonstrates that Ca 2+ /CaM-activated PDE1A activity is a key regulator of cross-talk between cAMP and Ca 2+ messenger molecules [14] and that a balance within cells between Ca 2+ -activated counteracting enzymes, ACs and PDEs, maintains optimal levels of function of these cells. For example, PDE1A (a Ca 2+ /CaM-activated enzyme) expression in retinal cells in which Ca 2+ /CaM-activated AC types drive cAMP production, modulates cAMP levels [15,16]. Similarly, in transgenic mice overexpressing Ca 2+ /CaM-activated neuronal AC Type 8 in LVC, the PDE1A affinity for cAMP becomes increased to limit the exaggerated cAMP production [17], shielding L-type Ca 2+ channels to prevent Ca 2+ overload [17,18].…”

cGMP-Phosphodiesterase Inhibition Prevents Hypoxia-Induced Cell Death Activation in Porcine Retinal Explants

“…In the retina, the cGMP performs an important role in the cascade of phototransduction which takes place in the photoreceptor (rods and cones) [28]. PDE1, PDE5 and PDE6 isoforms are found in mammalian retina [29] PDE5 and PDE6 share many structural, pharmacological and biochemical properties but differ in their cellular localization. While PDE6 is localized in photoreceptors, PDE5 is found in retinal and choroid vasculature, ganglion and bipolar cells [30].…”

Calcium-Dependent Increases in Protein Kinase-A Activity in Mouse Retinal Ganglion Cells Are Mediated by Multiple Adenylate Cyclases

“…However, cAMP levels are also influenced by phosphodiesterases. Indeed, retinal neurons express a calcium-dependent phosphodiesterase that could potentially mediate AC-independent changes in PKA activity [18].…”

“…To test directly for a role of the calcium-dependent phosphodiesterase PDE1, which is present in the ganglion cell layer [18], in depolarization induced PKA activity, we repeated these experiments in the presence of 8MM-IBMX, a specific inhibitor of calcium-activated PDE1. In contrast to IBMX, 8MM-IBMX did not lead to an increase in the baseline AKAR3 FRET ratio (Figure 5A,B).…”

“…Recent reports suggest that soluble adenylate cyclase (sAC) is also present in some neurons [13]-[16] although its presence in retinal neurons is controversial [16], [17]. Calcium-activated PDE1 is reported to be in the ganglion cell layer [18] but no calcium inhibited PDEs have been described.…”