CYSL-1 Interacts with the O2-Sensing Hydroxylase EGL-9 to Promote H2S-Modulated Hypoxia-Induced Behavioral Plasticity in C. elegans

Abstract

SUMMARY The C. elegans HIF-1 proline hydroxylase EGL-9 functions as an O2-sensor in an evolutionarily conserved pathway for adaptation to hypoxia. H2S accumulates during hypoxia and promotes HIF-1 activity, but how H2S signals are perceived and transmitted to modulate HIF-1 and animal behavior is unknown. We report that the experience of hypoxia modifies a C. elegans locomotive behavioral response to O2 through the EGL-9 pathway. From genetic screens to identify novel regulators of EGL-9-mediated behavioral plasticity, we isolated mutations of the gene cysl-1, which encodes a C. elegans homolog of sulfhydrylases/cysteine synthases. Hypoxia-dependent behavioral modulation and H2S-induced HIF-1 activation require the direct physical interaction of CYSL-1 with the EGL-9 C-terminus. Sequestration of EGL-9 by CYSL-1 and inhibition of EGL-9-mediated hydroxylation by hypoxia together promote neuronal HIF-1 activation to modulate behavior. These findings demonstrate that CYSL-1 acts to transduce signals from H2S to EGL-9 to regulate O2-dependent behavioral plasticity in C. elegans.

Hydrogen sulfide as an oxygen sensor

“…The beneficial effects of H 2 S in treating ischemia/reperfusion injury and in pre-and postconditioning have been well documented, and it has been suggested that the beneficial effects of exogenous H 2 S are due to mimicking transient hypoxia, which is also used in conditioning (128). It is also evident that H 2 S is involved in long-term O 2 sensing through its inhibitory effects on hypoxia inducible factor (HIF)-1a expression (70,148,149,188), although opposite effects have also been reported (17,91,93). In an elegant study, Ma et al (93) identified a novel genetic pathway where an increase in H 2 S produced by prolonged (24 h) hypoxia increases HIF-1 expression in C. elegans.…”

“…It is also evident that H 2 S is involved in long-term O 2 sensing through its inhibitory effects on hypoxia inducible factor (HIF)-1a expression (70,148,149,188), although opposite effects have also been reported (17,91,93). In an elegant study, Ma et al (93) identified a novel genetic pathway where an increase in H 2 S produced by prolonged (24 h) hypoxia increases HIF-1 expression in C. elegans. They showed that H 2 S promotes the interaction of CYSL-1 with EGL-9, thereby removing the inhibitory effect of EGL-9 on HIF-1.…”

CYP-13A12 of the nematode Caenorhabditis elegans is a PUFA-epoxygenase involved in behavioural response to reoxygenation

“…The O2-ON response of young adult fat-2(wa17) (n>50 for each treatment) was continuously measured using a multi-worm tracker with a gasflow chamber system and quantified by customized MatLab algorithms as previously described [4]. For characterizing the locomotive behaviour of wild-type and fat-3(wa22), we determined the worm's speed and body bend frequency according to Hart, 2006 [30].…”

“…The nematode C. elegans can survive at a wide range of oxygen concentrations, but exhibits an aerotaxis behaviour prompting the worms to migrate to their preferred oxygen concentration of about 10 % [2]. Upon anoxia/reoxygenation, C. elegans shows the so-called "O2-ON" behavioural response that is characterised by a rapidly increased locomotion speed [3,4]. Recent studies suggest that evolutionarily conserved pathways contribute to ischemiareperfusion injury in mammalian cells and to the O2-ON response in C. elegans [5].…”

“…Prolyl hydroxylation regulates HIF (hypoxia-inducible transcription factor) levels in C. elegans as well as in mammals and, thus, links hypoxia to HIF-mediated physiological responses [6][7][8][9][10]. EGL-9 inactivation blocks the O2-ON response of C. elegans [3,4]. A screen for mutations restoring the defective O2-ON response in an EGL-9 deficient strain, egl-9(n586), identified a gain-offunction allele of the cyp-13A12 gene that encodes a CYP (cytochrome P450) enzyme [5].…”