SummaryAdhesion class G protein-coupled receptors (aGPCR) form the second largest group of seven-transmembrane-spanning (7TM) receptors whose molecular layout and function differ from canonical 7TM receptors. Despite their essential roles in immunity, tumorigenesis, and development, the mechanisms of aGPCR activation and signal transduction have remained obscure to date. Here, we use a transgenic assay to define the protein domains required in vivo for the activity of the prototypical aGPCR LAT-1/Latrophilin in Caenorhabditis elegans. We show that the GPCR proteolytic site (GPS) motif, the molecular hallmark feature of the entire aGPCR class, is essential for LAT-1 signaling serving in two different activity modes of the receptor. Surprisingly, neither mode requires cleavage but presence of the GPS, which relays interactions with at least two different partners. Our work thus uncovers the versatile nature of aGPCR activity in molecular detail and places the GPS motif in a central position for diverse protein-protein interactions.

Cadmium is a widely distributed toxic environmental pollutant. Using proton NMR spectroscopy and UPLC-MS, we obtained metabolic profiles from the model organism Caenorhabditis elegans exposed to sublethal concentrations of cadmium. Neither in the presence nor absence of cadmium did the metallothionein status (single or double mtl knockouts) markedly modulate the metabolic profile. However, independent of strain, cadmium exposure resulted in a decrease in cystathionine concentrations and an increase in the nonribosomally synthesized peptides phytochelatin-2 and phytochelatin-3. This suggests that a primary response to low levels of cadmium is the differential regulation of the C. elegans trans-sulfuration pathway, which channels the flux from methionine through cysteine into phytochelatin synthesis. These results were backed up by the finding that phytochelatin synthase mutants (pcs-1) were at least an order of magnitude more sensitive to cadmium than single or double metallothionein mutants. However, an additive sensitivity toward cadmium was observed in the mtl-1; mtl-2; pcs-1 triple mutant.

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder characterized by progressive muscle degeneration and weakness due to mutations in the dystrophin gene. The symptoms of DMD share similarities with those of accelerated aging. Recently, hydrogen sulfide (H2S) supplementation has been suggested to modulate the effects of age-related decline in muscle function, and metabolic H2S deficiencies have been implicated in affecting muscle mass in conditions such as phenylketonuria. We therefore evaluated the use of sodium GYY4137 (NaGYY), a H2S-releasing molecule, as a possible approach for DMD treatment. Using the dys-1(eg33) Caenorhabditis elegans DMD model, we found that NaGYY treatment (100 µM) improved movement, strength, gait, and muscle mitochondrial structure, similar to the gold-standard therapeutic treatment, prednisone (370 µM). The health improvements of either treatment required the action of the kinase JNK-1, the transcription factor SKN-1, and the NAD-dependent deacetylase SIR-2.1. The transcription factor DAF-16 was required for the health benefits of NaGYY treatment, but not prednisone treatment. AP39 (100 pM), a mitochondria-targeted H2S compound, also improved movement and strength in the dys-1(eg33) model, further implying that these improvements are mitochondria-based. Additionally, we found a decline in total sulfide and H2S-producing enzymes in dystrophin/utrophin knockout mice. Overall, our results suggest that H2S deficit may contribute to DMD pathology, and rectifying/overcoming the deficit with H2S delivery compounds has potential as a therapeutic approach to DMD treatment.

Copper, though toxic in excess, is an essential trace element that serves as a cofactor in many critical biological processes such as respiration, iron transport, and oxidative stress protection. To maintain this balance between requirement and toxicity, biological systems have developed intricate systems allowing the preservation of homeostasis while ensuring delivery of copper to the appropriate cellular component. The nematode Caenorhabditis elegans was exploited to assess the effects of copper toxicity at the population level to identify key changes in life cycle traits including, lethality, brood size, generation time, growth, and life span. To enhance our understanding of the complexities of copper homeostasis at the genetic level, the expression profile and functional significance of a putative copper cytoplasmic metallochaperone cutc-1 were analyzed. Using quantitative PCR technology, cutc-1 was found to be downregulated with increasing CuSO(4) concentrations. However, although total (whole body) copper levels increased in nematodes exposed to elevated levels of copper, wild-type and knock down of cutc-1 by RNA-mediated interference (RNAi) were statistically indistinguishable. Nevertheless, RNAi of cutc-1 affected brood size, growth and induced a marked increase in protruding vulva and bagging phenotypes at higher copper exposures. This indicates that cutc-1 plays a crucial role in the protection from excess copper.