Controlling anoxic tolerance in adult Drosophila via the cGMP–PKG pathway

Abstract

Two naturally occurring strains of adult Drosophila melanogaster Meigen were used in this study: a rover strain homozygous for the for R allele (high PKG activity), and a sitter strain homozygous for for s (low PKG activity). These strains are isogenized natural polymorphisms of the foraging gene, located on the second chromosome (Sokolowski, 1980;Fitzpatrick et al., 2007). Additionally, the sitter mutant strain for s2, which was previously Accepted 12 April 2010 SUMMARY In this study we identify a cGMP-dependent protein kinase (PKG) cascade as a biochemical pathway critical for controlling lowoxygen tolerance in the adult fruit fly, Drosophila melanogaster. Even though adult Drosophila can survive in 0% oxygen (anoxia) environments for hours, air with less than 2% oxygen rapidly induces locomotory failure resulting in an anoxic coma. We use natural genetic variation and an induced mutation in the foraging (for) gene, which encodes a Drosophila PKG, to demonstrate that the onset of anoxic coma is correlated with PKG activity. Flies that have lower PKG activity demonstrate a significant increase in time to the onset of anoxic coma. Further, in vivo pharmacological manipulations reveal that reducing either PKG or protein phosphatase 2A (PP2A) activity increases tolerance of behavior to acute hypoxic conditions. Alternatively, PKG activation and phosphodiesterase (PDE5/6) inhibition significantly reduce the time to the onset of anoxic coma. By manipulating these targets in paired combinations, we characterized a specific PKG cascade, with upstream and downstream components. Further, using genetic variants of PKG expression/activity subjected to chronic anoxia over 6h, ~50% of animals with higher PKG activity survive, while only ~25% of those with lower PKG activity survive after a 24h recovery. Therefore, in this report we describe the PKG pathway and the differential protection of function vs survival in a critically low oxygen environment.

A cGMP-dependent protein kinase (PKG) controls synaptic transmission tolerance to acute oxidative stress at the Drosophila larval neuromuscular junction

“…These data suggest that the PKG pathway may contribute to an endogenous neuroprotective scheme that regulates neurological function in the presence of acute trauma. In favor of this hypothesis, PKG activity has been implicated in regulating the function of neural circuits, behavior, and susceptibility to stress in insect and vertebrate model systems, highlighting its potential as a novel target to rapidly relieve neural failure associated with traumatic brain insults (Armstrong et al 2010;Dawson-Scully et al 2010;Robertson and Sillar 2009).…”

“…The distinct mechanisms underlying the PKG pathway's potential for modulating neuronal function and ultimately neuroprotection during acute trauma remain only partially understood. Previous published data indicate a link between K ϩ conductance and PKG activity (Chai and Lin 2010;Dawson-Scully et al 2010;Renger et al 1999;White et al 1993), which leads to speculation that these ion channels are potential downstream targets of this intracellular signaling mechanism. However, which specific K ϩ channel(s) mediate PKG pathway effects is still a matter of debate.…”

Oxygen limits heat tolerance and drives heat hardening in the aquatic nymphs of the gill breathing damselfly Calopteryx virgo (Linnaeus, 1758)

“…A combination of hypoxia and heat apparently elicited a stronger response than heat alone. Such a response likely consist of an induction of the heat shock pathway, following the recognition that hypoxia and heat share several biochemical pathways (Baird et al, 2006), which includes activation of the cGMP-PKG pathway (Dawson-Scully et al, 2010). The cGMP-PKG pathway seems to be a major 'switch' controlling anoxia tolerance (Dawson-Scully et al, 2010), inducing escape behaviour, tracheal proliferation and arrest development in Drosophila embryo's and larvae (Wingrove and O'Farell, 1999).…”

Gene–environment interplay inDrosophila melanogaster: Chronic food deprivation in early life affects adult exploratory and fitness traits

“…Are sitters more plastic than rovers across environmental contexts, or does it depend on the type of adversity (e.g., nutritional, social) the individual experiences, and the timing of that adversity (chronic acute) during development? Previous studies have shown that sitters are more resistant to acute abiotic stressors, such as heat and hypoxia, than are rovers (69)(70)(71). The type of exposure used, chronic or acute, may explain which variant exhibits plasticity.…”