The role of prenylation in G-protein assembly and function

Higgins, Joyce B.; Casey, Patrick J.

doi:10.1016/s0898-6568(96)00071-x

Cited by 63 publications

(53 citation statements)

References 42 publications

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“…3B, c and d). These results are thus consistent with a model in which the ␤ 1 ␥ 2 dimer is geranylgeranylated in the cytosol by a cytoplasmic geranylgeranyltransferase (14) and then targeted to ER, prior to ␣-dependent transit to the PM.…”

Section: Replacement Of Cysteine With Serine In the Caax Motif Of Thesupporting

confidence: 89%

“…2B). Although prenylation of the ␤␥ complex has been reported to increase its affinity for the ␣ subunit (14,21), prenylation is not a strict requirement for heterotrimer formation. Consistent with this, none of the subunits in a crystallized ␣␤␥ complex contained lipid modifications; the C68S ␥ mutant produced in Sf9 cells was able to assemble with ␣ and ␤ subunits (17).…”

Section: Discussionmentioning

confidence: 99%

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Heterotrimer Formation, Together with Isoprenylation, Is Required for Plasma Membrane Targeting of Gऔγ

Takida

Wedegaertner

2003

Journal of Biological Chemistry

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Nascent ␤ and ␥ subunits of heterotrimeric G proteins need to be targeted to the cytoplasmic face of the plasma membrane (PM) in order to transmit signals. We show that ␤ 1 ␥ 2 is poorly targeted to the PM and predominantly localized to endoplasmic reticulum (ER) membranes when expressed in HEK293 cells, but co-expression of a G protein ␣ subunit allows strong PM localization of the ␤ 1 ␥ 2 . Furthermore, C-terminal isoprenylation of the ␥ subunit is necessary but not sufficient for PM localization of ␤ 1 ␥ 2 . Isoprenylation of ␥ 2 and localization of ␤ 1 ␥ 2 to the ER occurs independently of ␣ expression. Efficient PM localization of ␤ 1 ␥ 2 in the absence of co-expressed ␣ is observed when a site for palmitoylation, a putative second membrane targeting signal, is introduced into ␥ 2 . When a mutant of ␣ s is targeted to mitochondria, ␤ 1 ␥ 2 follows, consistent with an important role for ␣ in promoting subcellular localization of ␤␥. Heterotrimeric G proteins 1 are composed of ␣ and ␤␥ subunits. The ␤␥ complex only dissociates when denatured and hence is a functional monomer under physiological conditions. Upon receptor activation the ␤␥ dimer is freed from GTP-bound ␣ and relays signals to downstream molecules until it reassociates with GDP-bound ␣, re-forming the heterotrimer. To perpetuate this G protein cycle, the trimer must be tethered to the cytoplasmic face of the PM. This crucial subcellular localization is promoted by the covalent attachment of lipids to the subunits. Three lipid modifications have been found in G proteins, namely myristoylation and/or palmitoylation for the ␣ subunit and isoprenylation for the ␥ subunit. Myristoylation is the covalent attachment of a 14-carbon saturated myristate to an N-terminal glycine through an amide bond, whereas palmitoylation is a 16-carbon saturated palmitate linked to a cysteine via a thioester bond. Isoprenylation is a lipid modification in which an unsaturated, 15-carbon farnesyl isoprenoid or 20-carbon geranylgeranyl isoprenoid is linked to a cysteine, via a thioether bond.Mechanisms underlying the PM targeting of the ␣ subunit have been studied in some detail (1-3). The available data suggest a model in which myristoylation and/or binding to ␤␥ subunits constitutes an initial membrane targeting signal for the ␣ subunit. Subsequently, palmitoylation functions as a second signal that specifies localization to the PM. In contrast to the ␣ subunit, relatively less is known about how ␤␥ is targeted to the PM. Either a 15-carbon farnesyl or 20-carbon geranylgeranyl isoprenoid is linked to a cysteine residue in the so-called CAAX motif in the C terminus of the ␥ subunit (4, 5). The CAAX box (where C is a cysteine, A is commonly an aliphatic amino acid, and X can be one of several amino acids) is a consensus sequence for isoprenylation. The X residue is thought to specify which isoprenoid group will be linked to the cysteine. Among 12 human ␥ subunits thus far identified, ␥ 1 , ␥ 9 , and ␥ 11 have serine in the X position and are farnesylated, and the rest of ...

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Section: Replacement Of Cysteine With Serine In the Caax Motif Of Thesupporting

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Heterotrimer Formation, Together with Isoprenylation, Is Required for Plasma Membrane Targeting of Gऔγ

Takida

Wedegaertner

2003

Journal of Biological Chemistry

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“…Cutler et al (1996) speculated that the substrate for ERA1 could be a heterotrimeric G protein. Prenylation of G␥ is important to stabilize the complex at the membrane and for effector activation (Higgins and Casey, 1996;Fogg et al, 2001). We show here that Arabidopsis seeds lacking a complete heterotrimeric G protein complex have enhanced responsiveness to ABA when tested in the manner in which the era1 mutants were originally screened and found.…”

Section: Discussionmentioning

confidence: 99%

Role of a Heterotrimeric G Protein in Regulation of Arabidopsis Seed Germination

et al. 2002

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Seed germination is regulated by many signals. We investigated the possible involvement of a heterotrimeric G protein complex in this signal regulation. Seeds that carry a protein null mutation in the gene encoding the alpha subunit of the G protein in Arabidopsis (GPA1) are 100-fold less responsive to gibberellic acid (GA), have increased sensitivity to high levels of Glc, and have a near-wild-type germination response to abscisic acid and ethylene, indicating that GPA1 does not directly couple these signals in germination control. Seeds ectopically expressing GPA1 are at least a million-fold more responsive to GA, yet still require GA for germination. We conclude that the GPA1 indirectly operates on the GA pathway to control germination by potentiation. We propose that this potentiation is directly mediated by brassinosteroids (BR) because the BR response and synthesis mutants, bri1-5 and det2-1, respectively, share the same GA sensitivity as gpa1 seeds. Furthermore, gpa1 seeds are completely insensitive to brassinolide rescue of germination when the level of GA in seeds is reduced. A lack of BR responsiveness is also apparent in gpa1 roots and hypocotyls suggesting that BR signal transduction is likely coupled by a heterotrimeric G protein at various points in plant development.Seeds integrate many intrinsic signals to control germination (Koornneef et al., 2002). For example, since the original observation by Chrispeels and Varner (1966), it has been repeatedly shown that GA induces germination and that abscisic acid (ABA) antagonizes the GA effect (Koornneef and Van der Veen, 1980;Karssen et al., 1989; Gilroy and Jones, 1994;Ritchie and Gilroy, 1998;Lovegrove and Hooley, 2000). Seed germination of GA synthesis mutants can be rescued by the application of GA and ABA synthesis and insensitive mutants lack the ABA inhibition of GA-induced germination as well as being viviparous (Koornneef et al., 1982(Koornneef et al., , 1984 Finkelstein and Somerville, 1990;Koornneef and Karssen, 1994;Leon-Kloosterziel et al., 1996). Brassinosteroid (BR) probably acts downstream of GA because BR is able to rescue germination of GA-deficient (Steber and McCourt, 2001) and GA response (Steber et al., 1998) mutant seeds. These authors argue that the BR input is likely to reside upstream of ABA's attenuating effect on GA-induced germination because BR synthesis and response mutants have slightly altered ABA sensitivity.The inhibitory effect of high concentrations of sugars on germination may occur via ABA. The evidence supporting this comes from measurements of ABA in Glc-treated seedlings (Arenas-Huertero et al., 2000) and from the observation that ABA synthesis and response mutants are insensitive to Glc (Laby et al., 2000;Rook et al., 2001). Ethylene controls the Glc inhibition of germination (Zhou et al., 1998). Evidence supporting this includes the observations that high concentrations of ethylene antagonize the Glc repression of germination (Ghassemian et al., 2000), the ctr1 (constitutive ethylene response mutant; Gibs...

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“…The regulation of G-protein cellular localization and signaling is a lipid-mediated mechanism (61)(62)(63). The majority of G-protein subunits (G ␥ s) are modifi ed with a thioether-linked isoprenoid geranylgeranyl (C20) attached to Cys residues within the C-terminal "CAAX" box (C is Cys, A is any aliphatic amino acid, and X is the carboxyl terminal residue in which the single cysteine residue is modifi ed with either farnesyl or geranylgeranyl) ( 64 ).…”

Section: Pla2 and Atmentioning

confidence: 99%

Lipid second messengers and related enzymes in vertebrate rod outer segments

Giusto

Pasquaré

Salvador

et al. 2010

Journal of Lipid Research

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outer segment of the cell is comprised of a stack of many hundreds of densely packed discs, each of which represents a double layer of infolded plasma membrane. It has been suggested that phospholipid moieties in these membranes are metabolically active and are closely involved in the generation of physiological mediators. Modifi cations in the metabolism of photoreceptor membrane glycerolipids have been linked to the transduction of visual stimuli ( 3 ). Rod outer segment (ROS) membranes are composed of 50% protein and 50% lipid, by weight ( 2 ). Phospholipids and cholesterol represent nearly 90-95% and 4-6% (w/w) of total lipids, respectively. Rhodopsin accounts for at least 80-85% (w/w) of the total proteins ( 4-6 ) in disc ROS membranes. The rest are mainly proteins involved in phototransduction. The composition of mammalian ROS membrane phospholipids indicates that the major phospholipids are phosphatidylethanolamine (PE) and phosphatidylcholine (PC), along with relatively large amounts of phosphatidylserine (PS) (15%). Small amounts (less than 1% each) of sphingomyelin, phosphatidylinositol (PI) and phosphatidic acid (PA) are found in these membranes ( 7-13 ). In vertebrates, cholesterol (exclusively as the free sterol) is the principal neutral lipid, comprising The vertebrate photoreceptor cell is composed of different cellular compartments [outer segment (OS), inner segment (IS), and synaptic terminal (ST)], all of which differ in their lipid and protein content ( 1, 2 ). The photoreceptor is a highly specialized cell that responds to light stimulus and transmits this response to adjoining neurons for ultimate relay to the visual centers of the brain. TheThis work was supported

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The role of prenylation in G-protein assembly and function

Cited by 63 publications

References 42 publications

Heterotrimer Formation, Together with Isoprenylation, Is Required for Plasma Membrane Targeting of Gऔγ

Heterotrimer Formation, Together with Isoprenylation, Is Required for Plasma Membrane Targeting of Gऔγ

Role of a Heterotrimeric G Protein in Regulation of Arabidopsis Seed Germination

Lipid second messengers and related enzymes in vertebrate rod outer segments

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