Probable occurrence of toxin-susceptible G proteins in the nematode Caenorhabditis elegans

A cGAL-UAS bipartite expression toolkit for Caenorhabditis elegans sensory neurons

Animals integrate sensory information from the environment and display various behaviors in response to external stimuli. In Caenorhabditis elegans hermaphrodites, 33 types of sensory neurons are responsible for chemosensation, olfaction, and mechanosensation. However, the functional roles of all sensory neurons have not been systematically studied due to the lack of facile genetic accessibility. A bipartite cGAL-UAS system has been previously developed to study tissue- or cell-specific functions in C. elegans. Here, we report a toolkit of new cGAL drivers that can facilitate the analysis of a vast majority of the 60 sensory neurons in C. elegans hermaphrodites. We generated 37 sensory neuronal cGAL drivers that drive cGAL expression by cell-specific regulatory sequences or intersection of two distinct regulatory regions with overlapping expression (split cGAL). Most cGAL-drivers exhibit expression in single types of cells. We also constructed 28 UAS effectors that allow expression of proteins to perturb or interrogate sensory neurons of choice. This cGAL-UAS sensory neuron toolkit provides a genetic platform to systematically study the functions of C. elegans sensory neurons.

Second messengers mediating mechanical responses to the FARP GYIRFamide in the fluke Fasciola hepatica

Spontaneous phasic contractions recorded from isolated body strips of Fasciola hepatica were increased in frequency and amplitude by GYIRFamide, an FMRFamide-related peptide (FaRP). Superfusion with guanosine 5'-O-(2-thiodiphosphate) (100 microM, n = 5) reduced the effects of GYIRFamide on both frequency (by 82%) and amplitude (by 75%). The adenylate cyclase inhibitor MDL-12330A (25 microM) increased spontaneous activity. MDL-12330A completely inhibited the frequency response to GYIRFamide and reduced the amplitude response by 66% as measured relative to this elevated basal activity (n = 6). Inhibition of phospholipase C (PLC) with neomycin sulfate (1 mM) had no direct effect on activity but reduced the frequency response to GYIRFamide by 64% and the amplitude increase by 95% (n = 9). The protein kinase C (PKC) inhibitor chelerythrine chloride (10 microM) also reduced frequency and amplitude responses by 98 and 99%, respectively, without affecting basal contractility (n = 5). Phorbol 12-myristate 13-acetate, an activator of PKC, increased contraction frequency and amplitude (n = 6). It was concluded that GYIRFamide stimulates mechanical activity in F. hepatica through a G protein, via a PLC- and PKC-dependent second messenger pathway.

Isoprenylation of polypeptides in the nematode Caenorhabditis elegans

Covalent modification of eucaryotic proteins, involving addition of isoprenyl groups, is a widespread phenomenon. Here we provide direct evidence for this form of covalent modification in the free-living nematode, Caenorhabditis elegans. Following incubation in the presence of [3H]mevalonolactone, specific C. elegans polypeptides became labelled in both aqueous and detergent (Triton X-114)-enriched extracts. Chemical and GC-MS analysis of modifying groups, cleaved from C. elegans polypeptides, revealed that geranylgeranylation and, to a lesser extent, farnesylation of target polypeptides occurred. Immunoblot analysis provided preliminary evidence that the ras-like let-60 polypeptide was a target for isoprenylation in C. elegans.

Fatty acylation of polypeptides in the nematode Caenorhabditis elegans

Covalent modification of eucaryotic proteins, involving addition of fatty acyl groups, is a widespread phenomenon. Here we describe the occurrence of this form of covalent modification in the free-living nematode, Caenorhabditis elegans. Following incubation in the presence of either [3H]-myristic acid or [3H]-palmitic acid, specific C. elegans polypeptides became labelled. Chemical analysis revealed that following incubation of C. elegans with [3H]-myristic acid, polypeptides became labelled with myristoyl, palmitoyl or stearoyl moieties; after incubation with [3H]-palmitic acid, palmitoyl or stearoyl moieties were incorporated into polypeptides. Fatty acyl groups were linked to target polypeptides, predominantly through alkali-labile thioester or ester linkages and acid-labile amide linkages. Where myristoylation involved an amide linkage, the modified amino acid was usually glycine. Preliminary immunological evidence indicated that heterotrimeric GTP-binding protein alpha subunit(s) are possible target(s) for acylation in C. elegans.

Structure and expression of the gsa-1 gene encoding a G protein alpha(s) subunit in C. elegans

The heterotrimeric guanine nucleotide-binding proteins (G proteins) act as switches in the signal transduction from cell surface receptors to a variety of effectors. Among them, Gs proteins stimulate adenylate cyclase activities and regulate ion channels in mammals. We identified the gsa-1 gene encoding a G protein alpha subunit in the nematode Caenorhabditis elegans. The predicted product consists of 375 amino acid residues, 66% of which are identical with those of a mammalian Gs(alpha) subunit. The gsa-1 gene was physically mapped near the left end of chromosome I. A gsa-1/lacZ fusion gene was expressed in many cells in embryos, larvae and adults, including neurons, body wall muscle cells and muscle cells of the pharynx and the vulva. The results presents a basis for genetic studies of the gsa-1 gene.

Molecular cloning and functional expression of a serotonin receptor from Caenorhabditis elegans

A cDNA encoding a serotonin receptor has been isolated from a Caenorhabditis elegans mixed stage cDNA library. The nematode serotonin receptor, designated 5HT-Ce, was permanently expressed in murine Ltk-cells, where it mediates adenylate cyclase attenuation. Sequence analysis and the pharmacological profiles demonstrate its relatedness not only to Drosophila and Lymnae 5HT receptors but also to mammalian 5HT1a receptors. The 5HT-Ce-gene does not map close to the position of any known serotonergic mutations.

Evidence for a G protein system in the tegumental brush border plasma membrane of Hymenolepis diminuta

Guanine nucleotide-binding regulatory proteins (G proteins) mediate the transduction of signals from cell-surface receptors to intracellular effector enzymes. G protein alpha-subunits are routinely identified (and partially characterized) on the basis of their susceptibility to NAD(+)-dependent ADP-ribosylation NAD(+)-dependent ADP-ribosylation catalysed by cholera and/or pertussis toxins. Analysis of purified tegumental brush border plasma membrane from Hymenolepis diminuta by relevant methodologies has revealed the presence of a 42 kDa putative G protein alpha-subunit that is susceptible to ADP-ribosylation by both cholera and pertussis toxins. This polypeptide shows no definite resemblance to any of the four major mammalian G protein classes on the basis of M(r) and toxin-susceptibility. These results provide evidence for the existence of a tegumental G protein-linked signal transduction system in H. diminuta.