Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 53, Issue 5 B380-B390, Copyright © 1998 by The Gerontological Society of America
Age-specific modulation of light production potential, and alkaline phosphatase and protein tyrosine kinase activities in various age mutants of Caenorhabditis elegans
JR Vanfleteren, BP Braeckman, I Roelens and A De Vreese
Department of Biology, University of Gent, Belgium. [email protected]
Previous work has shown that reduction-of-function mutations in the genes
daf-2 and age-1 can increase adult life (Age phenotype) of Caenorhabditis
elegans and that certain daf-12 alleles considerably amplify this effect in
daf-2; daf-12 doubles. We have measured the light production potential
(LPP) and alkaline phosphatase (ALP) and protein tyrosine kinase (PTK)
activity levels as suitable biochemical markers to further investigate
genetic interactions between these genes. The light production assay
measures superoxide anion production by freeze-thawed worms in assay medium
containing sufficient amounts of nicotineamide adenine dinucleotide,
reduced form (NADH) and nicotineamide adenine dinucleotide phosphate,
reduced form (NADPH) to drive the chemiluminescent reaction at maximal
speed, and 5 mM cyanide to fully repress cytosolic superoxide dismutase
(SOD). This assay thus provides an estimate of the maximum output of the
metabolic pathways involved at the instant of freeze-fixation, and under
the condition of the assay. LPP and PTK activities decreased similarly in
daf-12(m20), and a control strain that had wild-type alleles of daf-12,
age-1, and daf-2. The age-dependent decrease of LPP and PTK was reduced in
age- 1(hx542) and age-1(hx542); daf-2(e1370), and virtually absent in daf-
2(e1370) and daf-2(e1370); daf-12(m20) mutant worms. ALP activity increased
with age in non-Age genotypes and showed little, if any, age- dependent
alteration in daf-2(e1370) and daf-2(e1370); daf-12(m20) mutant worms.
Mutation in both age-1 and daf-2 caused no stronger phenotype than a single
mutation as estimated by LPP, PTK, and ALP. We propose that (a) daf-2 is
the major effector of metabolic activity during adult life, (b) daf-2
downregulates metabolic activity with increasing age, and (c) daf-12
stimulates oxygen consumption independently of daf-2.
