Heterotrimeric G proteins sit at the cytoplasmic face of membranes and transduce signals. Palmitoylation occurs on most of the alpha subunits in the family of heterotrimeric G proteins. During an activation cycle, G alpha subunits communicate with G beta/gamma subunits, receptors, effectors and RGS proteins with palmitoylation modulating many of these protein interactions. In addition, palmitoylation can localize proteins to and within specific membrane sites. The localization of a splice variant of G alpha s, XL alpha s, to the Golgi complex is due, in part, to palmitoylation of cysteine residues adjacent to a Golgi targeting signal. Within membranes, palmitoylation can target proteins to microdomains, characterized by their resistance to detergents and enrichment in sphingolipids and cholesterol. G proteins are found in these microdomains, named rafts. Depletion of cellular cholesterol or sphingolipids disrupted the raft localization of G alpha s, but receptor-activated signaling through Gs remained intact suggesting that raft localization is not required for this function of Gs. Palmitoylation is a reversible modification with an increase in palmitate turnover on the G alpha subunit upon activation by a receptor. The enzymes responsible for reversible thioacylation have been elusive. A strong candidate for the thioesterase that removes palmitate is the 25-kDa protein, acyl-protein thioesterase 1 (APT1). Both APT1 and an isoform, APT2, (67% identical) are soluble proteins and expressed ubiquitously. The crystal structure of the human form of APT1 was solved to 1.8 angstrom resolution and showed that APT1 is a member of the alpha/beta hydrolase family, which includes other acylhydrolases such as the palmitoyl protein thioesterase. APT1 appears to be dimeric with the substrate-binding pocket and active site occluded by the dimer interface suggesting that dissociation occurs upon interaction with the substrate.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Intramural Research (Z01)
Project #
1Z01DK043010-07
Application #
6432126
Study Section
(MDB)
Project Start
Project End
Budget Start
Budget End
Support Year
7
Fiscal Year
2000
Total Cost
Indirect Cost
Name
U.S. National Inst Diabetes/Digst/Kidney
Department
Type
DUNS #
City
State
Country
United States
Zip Code
Hiol, Abel; Davey, Penelope C; Osterhout, James L et al. (2003) Palmitoylation regulates regulators of G-protein signaling (RGS) 16 function. I. Mutation of amino-terminal cysteine residues on RGS16 prevents its targeting to lipid rafts and palmitoylation of an internal cysteine residue. J Biol Chem 278:19301-8
Bahia, Daljit S; Sartania, Nana; Ward, Richard J et al. (2003) Concerted stimulation and deactivation of pertussis toxin-sensitive G proteins by chimeric G protein-coupled receptor-regulator of G protein signaling 4 fusion proteins: analysis of the contribution of palmitoylated cysteine residues to the GAP activity o J Neurochem 85:1289-98
Osterhout, James L; Waheed, Abdul A; Hiol, Abel et al. (2003) Palmitoylation regulates regulator of G-protein signaling (RGS) 16 function. II. Palmitoylation of a cysteine residue in the RGS box is critical for RGS16 GTPase accelerating activity and regulation of Gi-coupled signalling. J Biol Chem 278:19309-16
Waheed, Abdul A; Jones, Teresa L Z (2002) Hsp90 interactions and acylation target the G protein Galpha 12 but not Galpha 13 to lipid rafts. J Biol Chem 277:32409-12
Miura, Y; Hanada, K; Jones, T L (2001) G(s) signaling is intact after disruption of lipid rafts. Biochemistry 40:15418-23
Ugur, O; Jones, T L (2000) A proline-rich region and nearby cysteine residues target XLalphas to the Golgi complex region. Mol Biol Cell 11:1421-32
Devedjiev, Y; Dauter, Z; Kuznetsov, S R et al. (2000) Crystal structure of the human acyl protein thioesterase I from a single X-ray data set to 1.5 A. Structure 8:1137-46
Adam, L; Bouvier, M; Jones, T L (1999) Nitric oxide modulates beta(2)-adrenergic receptor palmitoylation and signaling. J Biol Chem 274:26337-43