102
G.N. Somera et al.
T. bernacchii (Hofmann and Somero, in preparation). The heat shock
response entails the induction of synthesis of one or more types of
molecular chaperones, proteins that assist in the folding and
compartmentalization of other proteins [21]. All cells examined to date
have been found to contain several types of molecular chaperones which
are essential for facilitating protein synthesis and maturation under normal
(nonstressful) cellular conditions. In addition to these constitutively
expressed chaperones, stress-induced chaperones ("heat shock" or "stress"
proteins) also have been found in all organisms examined. Stress-induced
chaperones prevent aggregation of unfolded proteins and, therefore, can be
viewed as an important "rescue" mechanism for helping to restore the
native structure of proteins damaged by environmental stress, such as that
resulting from exposure to high temperatures.
To investigate the heat shock response in T. bernacchii, we employed an
in vivo protein synthesis protocol that has been used successfully to study
the induction of heat shock proteins in several other species of fishes
[22,23]. This method involves the injection of specimens with a mixture of
35S-labeled methionine and cysteine, followed by exposure of the animals
to a range of temperatures, including temperatures predicted to be high
enough to induce the heat shock response. Following 2 h of exposure to
test temperatures, the animals are returned to a normal physiological
temperature and protein synthesis is allowed to occur for an additional
hour. At the end of this period, animals are sacrificed and the newly
synthesized proteins are visualized using SDS-PAGE and autoradiography.
When used in studies of temperate and tropical fishes, this method has
always yielded clear evidence for the induction of synthesis of heat shock
proteins, as shown for the eurythermal goby fish Gillichthys mirabilis in
Fig. 2.
Heat shock proteins of two size classes, 70 kDa and 90 kDa, are strongly
expressed in the gill tissue of this goby at 37 °e, but not at 25 °e. In
contrast to the response seen in G. mirabilis and several other marine
teleosts [23], we found no evidence of any induction of heat shock protein
synthesis in gill tissue (Fig. 2), brain, liver, spleen or muscle of T.
bernacchii exposed to high temperatures (6 °e, Fig. 2, or 9 °e, data not
shown). These negative findings represent the first case in which the heat
shock response has failed to be observed in an animal. Western analysis
showed that tissues of T. bernacchii contain constitutively expressed
molecular chaperones, in common with all other species, but our failure to
detect induction of stress-induced chaperones, i.e., heat shock proteins,
suggests that the capacity to increase chaperone synthesis in response to
G.N. Somera et al.
T. bernacchii (Hofmann and Somero, in preparation). The heat shock
response entails the induction of synthesis of one or more types of
molecular chaperones, proteins that assist in the folding and
compartmentalization of other proteins [21]. All cells examined to date
have been found to contain several types of molecular chaperones which
are essential for facilitating protein synthesis and maturation under normal
(nonstressful) cellular conditions. In addition to these constitutively
expressed chaperones, stress-induced chaperones ("heat shock" or "stress"
proteins) also have been found in all organisms examined. Stress-induced
chaperones prevent aggregation of unfolded proteins and, therefore, can be
viewed as an important "rescue" mechanism for helping to restore the
native structure of proteins damaged by environmental stress, such as that
resulting from exposure to high temperatures.
To investigate the heat shock response in T. bernacchii, we employed an
in vivo protein synthesis protocol that has been used successfully to study
the induction of heat shock proteins in several other species of fishes
[22,23]. This method involves the injection of specimens with a mixture of
35S-labeled methionine and cysteine, followed by exposure of the animals
to a range of temperatures, including temperatures predicted to be high
enough to induce the heat shock response. Following 2 h of exposure to
test temperatures, the animals are returned to a normal physiological
temperature and protein synthesis is allowed to occur for an additional
hour. At the end of this period, animals are sacrificed and the newly
synthesized proteins are visualized using SDS-PAGE and autoradiography.
When used in studies of temperate and tropical fishes, this method has
always yielded clear evidence for the induction of synthesis of heat shock
proteins, as shown for the eurythermal goby fish Gillichthys mirabilis in
Fig. 2.
Heat shock proteins of two size classes, 70 kDa and 90 kDa, are strongly
expressed in the gill tissue of this goby at 37 °e, but not at 25 °e. In
contrast to the response seen in G. mirabilis and several other marine
teleosts [23], we found no evidence of any induction of heat shock protein
synthesis in gill tissue (Fig. 2), brain, liver, spleen or muscle of T.
bernacchii exposed to high temperatures (6 °e, Fig. 2, or 9 °e, data not
shown). These negative findings represent the first case in which the heat
shock response has failed to be observed in an animal. Western analysis
showed that tissues of T. bernacchii contain constitutively expressed
molecular chaperones, in common with all other species, but our failure to
detect induction of stress-induced chaperones, i.e., heat shock proteins,
suggests that the capacity to increase chaperone synthesis in response to