Protein kinase and protein phosphatase expression in the central nervous system of G93A mSOD over-expressing mice

Abstract

The expressions of 78 protein kinases, 24 protein phosphatases and 31 phosphoproteins were investigated by Kinetworks™ analysis in brain and spinal cord tissue of transgenic mice over‐expressing G93A mutant superoxide dismutase (mSOD), a murine model of amyotrophic lateral sclerosis (ALS). In the brains of affected mSOD mice, we observed increased expression of cAMP‐dependent protein kinase (PKA, 111% increase compared with control), and protein phosphatase 2B Aα‐catalytic subunit (calcineurin, 109% increase), and reductions in the levels of PAK3 (76% decrease) and protein phosphatase 2C Cβ‐subunit (32% decrease). Increased Ser259 phosphorylation of Raf1 (126% increase) in mSOD mice correlated with higher expression of p73 Raf1 (147% increase). There was also increased p73 Raf1 (69% increase) and Ser259 phosphorylation (45% increase) in the spinal cords of mSOD mice. While adducin underwent enhanced phosphorylation (αS724, 90% increase; γS662, 290% increase) in mSOD brain, its phosphorylation was lower in the mSOD spinal cord (αS724, 53% decrease; γS662, 46% decrease). In spinal cords of affected mSOD mice, we also observed elevated expression of casein kinase 1δ (CK1δ, 157% increase), JAK2 (84% increase), PKA (183% increase), protein kinase C (PKC) δ (123% increase), p124 PKCµ (142% increase), and RhoA kinase (221% increase), and enhanced phosphorylation of extracellular regulated kinases 1 (ERK1, T202/Y204, 90% increase), and 2 (ERK2, T185/Y187, 73% increase), p38 MAP kinase (T180/Y182, 1570% increase), and PKBα (T308, 154% increase; S473, 61% increase). There was also reduced phosphorylation of RB (S780, 45% decrease; S807/S811, 65% decrease), Src (Y418, 63% decrease) and p40 SAPK/JNKβ (T183/Y185, 43% decrease). Variability in the expression of kinases, phosphatases and phosphorylation of their substrates was observed even in mutant animals having a similar phenotype. The expression and phosphorylation differences between mSOD and control mice were dissimilar to those between ALS patients and controls. This finding indicates that the activation of protein kinases and phosphoproteins is different with neuron loss in the mSOD mouse compared with that seen in patients with the sporadic form of ALS.