Open AccessProtein synthesis is lowered by 4EBP1 and eIF2-α signaling while protein degradation may be maintained in fasting, hypoxic Amazonian cichlid, Astronotus ocellatus
Author(s) -
Alicia A. Cassidy,
William R. Driedzic,
Derek Felipe Campos,
Waldir Heinrichs-Caldas,
Vera Maria Fonseca de Almeida-Val,
Adalberto Luís Val,
Simon G. Lamarre
Publication year - 2017
Publication title -
journal of experimental biology
Language(s) - English
Resource type - Journals
eISSN - 1477-9145
pISSN - 0022-0949
DOI - 10.1242/jeb.167601
Subject(s) - cichlid , protein degradation , hypoxia (environmental) , protein turnover , biology , protein metabolism , metabolic pathway , enzyme , protein biosynthesis , anabolism , metabolism , protease , biochemistry , chemistry , oxygen , fish <actinopterygii> , fishery , organic chemistry
The Amazonian cichlid, Astronotus ocellatus, is highly tolerant to hypoxia, and is known to reduce its metabolic rate by reducing the activity of energetically expensive metabolic processes when oxygen is lacking in their environment. Our objectives were to determine how protein metabolism is regulated in A. ocellatus during hypoxia. Fish were exposed to a stepwise decrease in air saturation (100%, 20%, 10% and 5%) for 2 hours at each level, and sampled throughout the experiment. A flooding dose technique using a stable isotope allowed us to observe an overall decrease in protein synthesis during hypoxia in liver, muscle, gill and heart. We estimate that this decrease in rates of protein synthesis accounts for a 20 to 36% decrease in metabolic rate, which would enable oscars to maintain stable levels of ATP and prolong survival. It was also determined for the first time in fish that a decrease in protein synthesis during hypoxia is likely controlled by signaling molecules (4EBP1 and eIF2-α), and not simply due to a lack of ATP. We could not detect any effects of hypoxia on protein degradation as the levels of NH4 excretion, indicators of the ubiquitin proteasome pathway, and enzymatic activities of lysosomal and non-lysosomal proteolytic enzymes were maintained throughout the experiment.