Decreased phosphorylation of NMDA receptor type 1 at serine 897 in brains of patients with Schizophrenia

Abstract

NMDA receptor hypofunction in schizophrenia has been inferred by a large number of clinical and preclinical observations; however, whether and how NMDA receptors are exactly involved in the pathogenesis of schizophrenia are still unknown and subject to interpretation. Here we show, in two independent samples of brains from patients with schizophrenia, a significant decrease in the phosphorylation level at serine 897 (S897) of the NMDA receptor type 1 (NR1) subunit. Our finding, together with a previous report that antipsychotics increase phosphorylation of NR1 at S897 in vivo, strongly suggests that insufficient phosphorylation at S897 may contribute to the neuronal pathology underlying schizophrenia.

Figure 1.

Decreased phosphorylation of NR1 at S897 in postmortem brain tissue obtained from the MRC Brain Bank. A, S897Ab specificity for the phosphorylated form of human NR1. Equal amounts of total protein extracts of human frontal cortex were resuspended in appropriate phosphatase reaction buffers. Four hundred units of lambda phosphatase (lane 2), 1 U of PP1 (lane 3), or 2 U of PP2A (lane 4) was added, and all samples, including the controls, were incubated for 30 min at 30°C. B, Phosphorylation of NR1 on S897 in frontal cortex of patients with schizophrenia (n = 10) and controls (n = 10) obtained from the MRC Brain Bank. One hundred micrograms of total protein extract were loaded in each lane. Representative immunoblots are shown, probed with S897NR1 antibody (1:1000), anti-NR1 antibody (1:1000), S831 GluR1 antibody (1:1000), S380 PTEN antibody (1:2000), and anti-tubulin (1:1000). C, Phosphorylation of NR1 on S897 in hippocampus of controls (n = 5) and schizophrenics (n = 4) obtained from the MRC Brain Bank. Representative immunoblots are shown, probed with S897NR1 antibody (1:1000), anti-NR1 antibody (1:1000), S831 GluR1 antibody (1:1000), S845 GluR1 antibody (1:1000), S380 PTEN antibody (1:2000), and anti-tubulin (1:1000).

Figure 2.

Decreased phosphorylation of NR1 at S897 in postmortem brain tissue obtained from the Stanley Brain Bank. A, B, Phosphorylation of NR1 on S897 in frontal cortex of patients with schizophrenia (n = 14), bipolar mood disorder (n = 15), major depression (n = 14), and controls (n = 15) obtained from the Stanley Consortium Brain Bank. The decrease in phosphorylation of NR1 on S897 is specific to patients with schizophrenia. Fifty micrograms of total protein extract were loaded in each lane, and samples were examined blind to the affected status (A) as well as after the ID codes were released (B). Representative immunoblots are shown, probed with S897 NR1 antibody (1:1000), anti-NR1 antibody (1:1000), S831 GluR1 antibody (1:1000), S845 GluR1 antibody (1:1000), S380 PTEN antibody (1:2000), and anti-tubulin (1:1000). In all cases, graphs represent the means and SEs of optical densities reflecting the corrected S897 to total NR1 levels.