Palmitoylation of the GluR6 kainate receptor.

Abstract

The G-protein-coupled metabotropic glutamate receptor mGluRla and the ionotropic glutamate receptor GluR6 were examined for posttranslational palmitoylation. Recombinant receptors were expressed in baculovirusinfected insect cells or in human embryonic kidney cells and were metabolically labeled with [3HI palmitic acid. The metabotropic mGluRla receptor was not labeled whereas the GluR6 kainate receptor was labeled after incubation with Receptors for the excitatory neurotransmitter L-glutamate can be grouped into two major families, ionotropic receptors and metabotropic receptors. The metabotropic glutamate receptors are G-protein-linked receptors coupled to effectors such as phospholipase C and adenylyl cyclase, whereas the ionotropic receptors form homomeric and heteromeric ligandgated ion channels permeable to mono-and divalent cations. A further subdivision of the ionotropic family can be made on the basis of agonist selectivity, giving the a-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) (GluR1-4, also called GluRA-D), kainate (GluR5-7, KA-1, KA-2), and Nmethyl-D-aspartate (NMDA) classes of receptors (1).Several studies have examined various aspects of the structure and function of the GluR6 kainate receptor (2-10). The activity of GluR6 channels can be modulated by protein kinase A (6, 7) and protein kinase C (PKC) (8). Site-directed mutagenesis of asparagine-linked glycosylation sites (9-12) and epitope tagging studies (13) have been carried out to derive transmembrane topological models of kainate and AMPA receptors. In these models, a large extracellular aminoterminal domain is followed by either three or five transmembrane domains (TMDs), resulting in either case in a carboxyl terminus that is intracellular.Palmitoylation is a posttranslational modification whereby a C16 fatty acyl chain is covalently bound to a nascent protein in a post-endoplasmic reticulum or pre-Golgi compartment. The fatty acid can be attached to a serine, threonine, or cysteineThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. residue via an ester or thioester bond. In contrast to myristoylation, which occurs cotranslationally and without metabolic turnover (14), a rapid, dynamic turnover of palmitate has been demonstrated in several systems (15)(16)(17).Several G-protein-linked receptors, including rhodopsin (18) and 132-adrenergic (19)

KRIP6: A novel BTB/kelch protein regulating function of kainate receptors

“…This interpretation is consistent with previous evidence for both kainate (Bowie and Lang, 2002) and AMPA (Tang et al 1989;Bowie and Lange, 2002) receptors that different open states underlie the initial peak current and the steady-state current recorded at equilibrium. In addition, the independent effects of KRIP6 on peak and steady-state currents may reflect differences among channel populations in the phosphorylation (Raymond et al, 1993;Wang et al, 1993) or palmitoylation (Pickering et al, 1995) state of GluR6. Such post-translational modifications could functionally segregate GluR6 containing kainate receptors into different pools or vary accessibility to functional regulation by KRIP6.…”

Palmitoylation gates phosphorylation-dependent regulation of BK potassium channels

“…and I.C.M.R., unpublished work). For example, in ligand-gated GluR6 receptors, the identified sites of palmitoylation are flanked by potential PKC phosphorylation sites, and it has been reported that palmitoylation modifies PKC-mediated phosphorylation of GluR6 receptors (20). Thus, cross-talk between these major posttranslational regulatory pathways, at the level of a single ion channel polypeptide as reported here for BK channels, is likely to be of much broader significance to conditionally regulate a variety of other ion channels.…”

“…Protein phosphorylation is a fundamental mechanism to control ion channel function, and increasing evidence suggests that multiple ion channels are also regulated by palmitoylation (16)(17)(18)(19)(20)(21). We would predict that phosphorylationpalmitoylation cross-talk is likely to occur when sites of palmitoylation are flanked by sites of serine/threonine phosphorylation.…”

“…Catalytic subunit of PKAc was from Promega. The 8-CPT-cGMP, 8-CPT-cAMP, KT5823, chelerythrine chloride, KN-62, and PKI [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] were from Calbiochem.…”

“…1A). In many proteins, including other voltage-and ligand-gated ion channels (16)(17)(18)(19)(20)(21), cysteine residues are common targets for protein palmitoylation, the covalent attachment of a palmitate lipid to a cysteine residue via a thioester bond. Palmitoylation can exert diverse effects on protein function including allowing cytosolic protein domains to anchor to the plasma membrane (22)(23)(24).…”