Ventra C, Porcellini A, Feliciello A, Gallo A, Paolillo M, Mele E, Avvedimento V E, Schettini G
Dipartimento di Neuroscienze e della Comunicazione Interumana, Cattedra di Farmacologia, Università degli Studi di Napoli, Italy.
J Neurochem. 1996 Apr;66(4):1752-61. doi: 10.1046/j.1471-4159.1996.66041752.x.
We analyzed the expression and relative distribution of mRNA for the regulatory subunits (RIalpha, RIIalpha, and RIIbeta) and of 150-kDa RIIbeta-anchor proteins for cyclic AMP (cAMP)-dependent protein kinase (PKA) into discrete brain regions. The subcellular distribution of both holoenzyme and free catalytic subunit was evaluated in the same CNS areas. In the neocortex and corpus striatum high levels of RIIbeta paralleled the presence of specific RII-anchoring proteins, high levels of membrane-bound PKA holoenzyme, and low levels of cytosolic free catalytic activity (C-PKA). Conversely, in brain areas showing low RIIbeta levels (cerebellum, hypothalamus, and brainstem) we found an absence of RII-anchoring proteins, low levels of membrane-bound holoenzyme PKA, and high levels of cytosolic dissociated C-PKA. Response to cAMP stimuli was specifically evaluated in the neocortex and cerebellum, prototypic areas of the two different patterns of PKA distribution. We found that cerebellar holoenzyme PKA was highly sensitive to cAMP-induced dissociation, without, however, a consistent translocation of C-PKA into the nucleus. In contrast, in the neocortex holoenzyme PKA was mainly in the undissociated state and poorly sensitive to cAMP. In nuclei of cortical cells cAMP stimulated the import of C-PKA and phosphorylation of cAMP-responsive element binding protein. Taken together, these data suggest that RIIbeta (whose distribution is graded throughout the CNS, reaching maximal expression in the neocortex) may represent the molecular cue of the differential nuclear response to cAMP in different brain areas, by controlling cAMP-induced holoenzyme PKA dissociation and nuclear accumulation of catalytic subunits.
我们分析了环磷酸腺苷（cAMP）依赖性蛋白激酶（PKA）的调节亚基（RIα、RIIα和RIIβ）以及150-kDa RIIβ锚定蛋白的mRNA在离散脑区中的表达和相对分布。在相同的中枢神经系统区域评估了全酶和游离催化亚基的亚细胞分布。在新皮层和纹状体中，高水平的RIIβ与特定RII锚定蛋白的存在、高水平的膜结合PKA全酶以及低水平的胞质游离催化活性（C-PKA）平行。相反，在RIIβ水平较低的脑区（小脑、下丘脑和脑干），我们发现不存在RII锚定蛋白、膜结合全酶PKA水平较低以及胞质解离C-PKA水平较高。在新皮层和小脑这两个PKA分布不同模式的典型区域，专门评估了对cAMP刺激的反应。我们发现小脑全酶PKA对cAMP诱导的解离高度敏感，然而，C-PKA并没有持续易位到细胞核中。相比之下，在新皮层中，全酶PKA主要处于未解离状态，对cAMP不敏感。在皮层细胞核中，cAMP刺激了C-PKA的导入和cAMP反应元件结合蛋白的磷酸化。综上所述，这些数据表明，RIIβ（其分布在整个中枢神经系统中呈梯度变化，在新皮层中达到最大表达）可能通过控制cAMP诱导的全酶PKA解离和催化亚基的核积累，代表不同脑区对cAMP的差异性核反应的分子线索。
