Neuroscience Letters 389 (2005) 51–56 Phosphorylation of AMPA receptor subunits is differentially regulated by phospholipase A 2 inhibitors Caroline M´ enard a,∗ , Christian Patenaude a , Guy Massicotte a,b a D´ epartement de chimie-biologie, Universit´ e du Qu´ ebec ` a Trois-Rivi` eres, C.P. 500, Trois-Rivi` eres, Que., Canada G9A 5H7 b D´ epartement de pharmacologie, Facult´ e de m´ edecine, Universit´ e de Montr´ eal, Montr´ eal, Que., Canada Received 8 April 2005; received in revised form 3 June 2005; accepted 8 July 2005 Abstract Our laboratory recently discovered that the phosphorylation of subunits forming the alpha-amino-3-hydroxy-5-methylisoxazole-4- propionate (AMPA) subtype of glutamate receptors is regulated by constitutive phospholipase A 2 (PLA 2 ) activity in rat brain sections. In the present investigation, arachidonyl trifluoromethyl ketone (AACOCF3) and bromoenol lactone (BEL) were used to compare the influ- ence of calcium-dependent (cPLA 2 ) and calcium-independent (iPLA 2 ) enzymes on phosphorylation of AMPA and N-methyl-d-aspartate (NMDA) subtypes of glutamate receptors. Incubation of rat brain sections with 3 M BEL enhanced phosphorylation on the serine (Ser) 831 residue of the AMPA receptor GluR1 subunit in synaptosomal P2 fractions, whereas AACOCF3 at the same concentration resulted in increased phosphorylation on residues Ser880/891 of GluR2/3 subunits. These effects were restricted to the AMPA receptor subtype as no changes in phosphorylation were elicited on the NMDA receptor NR1 subunit. The effects of BEL and AACOCF3 were not occluded during blockade of protein phosphatases since AMPA receptor phosphorylation was still apparent in the presence of okadaic acid, indicating that the PLA 2 inhibitor-induced increase in AMPA receptor phosphorylation does not rely on a decrease in dephosphorylation reactions. However, pretreatment of rat brain sections with a cell-permeable protein kinase C (PKC) inhibitor prevented BEL- and AACOCF3-induced phosphorylation on the Ser831 and Ser880/891 sites of GluR1 and GluR2/3 subunits, respectively. These results suggest that constitutive cPLA 2 and iPLA 2 systems may differentially influence AMPA receptor properties and function in the rat brain through mechanisms involving PKC activity. © 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Phospholipases A 2 ; Glutamate receptor; Phosphorylation; Brain sections Phospholipases A 2 (PLA 2 s) are a large and diverse super- family of enzymes which primarily catalyze the hydrolysis of membrane phospholipids at the sn-2 position to generate lysophospholipids and free fatty acids [13]. These enzymes are well known for their involvement in the regulation of inflammation, immune function and smooth muscle con- traction through the production of arachidonic acid and Abbreviations: AACOCF3, arachidonyl trifluoromethyl ketone; AMPA, -amino-3-hydroxy-5-methylisoxazole-4-propionate; BEL, bromoenol lac- tone; NMDA, N-methyl-d-aspartate; PKC, protein kinase C; PLA 2 , phos- pholipase A 2 ; cPLA 2 , calcium-dependent phospholipase A 2 ; iPLA 2 , calcium-independent phospholipase A 2 ; PP, protein phosphatases; Ser, ser- ine ∗ Corresponding author. Tel.: +1 819 376 5053; fax: +1 819 376 5084. E-mail address: Caroline Menard@uqtr.ca (C. M´ enard). its subsequent metabolism to eicosanoids (prostaglandins, leukotrienes, etc.) via cyclooxygenase and lipoxygenase enzymes [13]. More than 19 isoforms of PLA 2 s have been identified so far and classified in three main groups, namely, the cytosolic calcium-dependent group (cPLA 2 ), the calcium-independent group (iPLA 2 ), and the secreted group. In the brain, cPLA 2 and iPLA 2 systems have attracted con- siderable attention because of their possible involvement in learning and memory [7], the formation of long-term poten- tiation [15], and the development of several neurological diseases [23]. Recent experimental results have provided evidence that constitutive iPLA 2 activity interacts with synaptic func- tion by modulating phosphorylation of the alpha-amino-3- hydroxy-5-methylisoxazole-4-propionate (AMPA) subtype 0304-3940/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2005.07.012