Pastuhov, S.Iv. et al. (2019) International Worm Meeting "Phosphatidylserine exposure mediated by ABC transporter activates the integrin signaling pathway promoting axon regeneration."

Hanafusa, H., Tsuge, A., Pastuhov, S.Iv., Matsumoto, K., Hisamoto, N., Shimizu, T.

[International Worm Meeting, 2019]

Following axon injury, a cascade of signaling events is triggered to initiate axon regeneration. However, the mechanisms regulating axon regeneration are not well understood at present. In Caenorhabditis elegans, axon regeneration utilizes many of the components involved in phagocytosis, including integrin and Rac GTPase. Here, we identify the transthyretin (TTR)- like protein TTR-11 as a component functioning in axon regeneration upstream of integrin. We show that TTR-11 binds to both the extracellular domain of integrin-? and phosphatidylserine (PS). Axon injury induces the accumulation of PS around the injured axons in a manner dependent on TTR-11, the ABC transporter CED-7, and the caspase CED-3. Furthermore, we demonstrate that CED-3 activates CED-7 during axon regeneration. Thus, TTR-11 functions to link the PS injury signal to activation of the integrin pathway, which then initiates axon regeneration.

Pastuhov, Strahil Iv et al. (2013) International Worm Meeting "Endocannabinoid AEA as injury signal in axon regeneration."

Pastuhov, Strahil Iv, Matsumoto, Kunihiro, Hisamoto, Naoki

[International Worm Meeting, 2013]

The endocannabinoid arachidonoyl ethanolamide (AEA) inhibits axon regeneration of D-type motor neurons in Caenorhabditis elegans by regulating the activity of the JNK MAP kinase cascade (Pastuhov SI et al (2012), Nat Commun. 3:1136). AEA levels are controlled through enzymatic synthesis and degradation. Our previous work demonstrated that inactivation of the AEA degradation pathway inhibits axon regeneration. For example, deletion mutation in the gene for fatty acid amide hydrolase (FAAH), the enzyme that inactivates AEA by hydrolysis, causes defect in axon regeneration due to accumulation of high levels of endogenous AEA. This time, we focused on the synthesis of AEA in axon regeneration. NAPE-1 is a worm homologue of NAPE-PLD, an enzyme involved in AEA synthesis. We found that the nape-1 null mutation suppressed the faah-1 defect in axon regeneration. Conversely, overexpression of nape-1 in D-type motor neurons by the unc-25 promoter inhibited axon regeneration after laser surgery. These results suggest that the inhibition of axon regeneration by NAPE-1 occurs at restricted area around the injured neuron. Interestingly, when nape-1 was overexpressed in touch receptor neurons by the mec-7 promoter, D-type motor neurons were able to regenerate after laser surgery, but their regenerating axons tended to make a sharp turn upon approaching the lateral midline, where axons of PLM touch neurons extend. These results suggest that high local levels of AEA inhibit axon regeneration and that a gradient of lower concentration affects the guidance of the regenerating axon.

Hernandez Cravero, Bruno et al. (2021) International Worm Meeting "Uncovering a novel endocannabinoid (2-AG) pathway required to modulate cholesterol metabolism in Caenorhabditis elegans"

Hernandez Cravero, Bruno, De Mendoza, Diego, Prez, Gaston, Vranych , Cecilia

[International Worm Meeting, 2021]

Cholesterol is an essential constituent of eukaryotes membranes and its derivate metabolites also serve as a signaling molecule that is crucial for growth, development and differentiation. Dysregulation of cholesterol metabolism is strongly associated with the development of cardiovascular disorders and neurodegeneration. Caenorhabditis elegans is especially suited to genetically study organismal orchestration of cholesterol metabolism. This worm requires exogenous cholesterol to survive and perturbations in cholesterol trafficking result in an early development larval arrest. Thus, tight regulation of cholesterol storage and distribution within the organism is critical. We have recently demonstrated that the endocannabinoid 2-arachidonoylglycerol (2-AG) plays a key role in C. elegans modulating sterol mobilization (Galles et al, Sci Rep. 2018; 6398). However, the mechanism by which 2-AG controls cholesterol trafficking in C. elegans is not known. Recent reports have shown that C. elegans has two cannabinoid-like receptors named NPR-19 and NPR 32, which are involved in nociception and regenerative axon navigation, respectively (Oakes et al, J. Neurosci. 2017; 2859, Pastuhov et al, Genes Cells. 2016; 696). Here we show that neither NPR-19 or NPR-32 are involved in 2-AG-mediated cholesterol trafficking. Furthermore, we found that the insulin-IGF1(IIS) signalling pathway is essential for the 2-AG suppression of larval arrest induced by cholesterol depletion. Studying the linkage between IIS and 2-AG we found two C. elegans single mutants, ocr-2 and osm-9, were insensitive to the 2-AG-mediated mobilization cholesterol in sterol-depleted worms. OCRs and OSM-9 proteins belong to C. elegans Transient Receptor Potential Vanilloid (TRPV) subfamily channels (Colbert et al, J. Neurosci. 1997; 8259). TRPV channels were previously reported as a sort of cannabinoid receptors in mammals (Ahluwalia et al, Eur J. Neurosci. 2003; 2611). Thus, we propose that OCR-2 and OSM-9 are endocannabinoid receptors in C. elegans, defining a novel signalling pathway mediated by 2-AG that modulates sterol metabolism in C. elegans.