Opposite roles of trehalase activity in heat-shock recovery and heat-shocksurvival in Saccharomyces cerevisiae

A variety of results has been obtained consistent with activation of neutra l trehalase in Saccharomyces cerevisiae through direct phosphorylation by c AMP-dependent protein kinase (PKA). A series of neutral trehalase mutant al leles, in which all evolutionarily conserved putative phosphorylation sites were changed into alanine, was tested for activation in vitro (by PKA) and in vivo (by glucose addition). None of the mutations alone affected the ac tivation ratio, whereas all mutations combined resulted in an inactive enzy me. All mutant alleles were expressed to similar levels, as shown by Wester n blotting. Several of the point mutations significantly lowered the specif ic activity. Using this series of mutants with different activity levels we show an inverse relationship between trehalase activity and heat-shock sur vival during glucose-induced trehalose mobilization. This is consistent wit h a stress-protective function of trehalose. On the other hand, reduction o f trehalase activity below a certain threshold level impaired recovery from a sublethal heat shock. This suggests that trehalose breakdown is required for efficient recovery from heat shock, and that the presence of trehalase protein alone is not sufficient for efficient heat-stress recovery.