Hsp Expresion En Bibalvos

ISJ 5: 135-161, 2008

ISSN 1824-307X

Review

HSP expression in bivalves

E Fabbri, P Valbonesi, S Franzellitti
Interdepartment Centre for Environmental Science Research, University of Bologna, campus of Ravenna, Italy

Accepted September 26, 2008

Abstract
One of the molecular responses which mostly contribute to the physiological plasticity of bivalves
is the heat shockresponse mediated by heat shock proteins (HSP). Variations of HSP response were
observed under environmental conditions, correlated with differences in environmental temperature
and degree of heterogeneity across geographic thermal gradients and through time. Laboratory
experiments characterized the expressions of different protein isoforms and coding genes, which are
induced by heat as aprototypical stimulus. Nevertheless, other physical and chemical factors
significantly induce HSP gene and protein expressions in bivalves, that can be different depending on
tissues and the nature of the insult. Multiple alignments of the deduced amino acid sequences
indicated that the bivalve HSP70 proteins share common structural and evolutionary features with the
mammalian HSP70, while someappear to be exclusive. The rate at which new findings are made
regarding the bivalve HSP response is still increasing. However, some major questions remain
unanswered. Among them, the possibility that the bivalve HSP response is related to cell signalling
pathways and acts as a component of the acute systemic response to stress is also discussed in this
review.
Key words: bivalves; HSP; HSPexpression; HSP phylogeny; HSP sequence; stress response

Introduction
organisms living at their physiological stress limit will
be affected by the continuous rise in temperature
predicted under climate change scenarios, and only
those endowed with sufficient defence mechanisms
will be able to survive.
The aim of this review is to outline the current
state of our knowledge of one of themolecular
responses which most contribute to the
physiological plasticity of bivalves, i.e., the heat
shock response mediated by heat shock proteins
(HSP), examined at the level of gene and protein
expressions. We also discuss structural features of
the HSP70 and HSP90 multigene families in
bivalves, and their phylogenetic relationships.
Traditionally the heat shock response has beenconsidered an intracellular phenomenon with little or
no association with intra/extracellular signalling. In
this review we want to draw attention to the fact that
the HSP response is related to cell signalling
pathways, and as it is a component of the acute
systemic response to stress, it is integrated with the
physiological stress response. These relationships
are presently under activeinvestigation in
mammals, and initial findings suggest that they may
also apply to bivalves (Lacoste et al., 2001a).

Living systems have evolved a variety of
strategies to respond to external or internal
environmental challenges. While these responses
are often behavioural or metabolic, a powerful
mechanism widely employed to maintain cellular
homeostasis under stress is the adjustment ofgene
expression. Due to their immobility, sessile
organisms in particular rely on this physiological
plasticity to adapt to environmental insults and
colonize rapidly fluctuating habitats. Bivalves living
in intertidal zones are one of the best examples of
ectotherms surviving highly stressful conditions,
facing exposure to natural changes in temperature,
salinity, and oxygenavailability exacerbated by the
extensive presence of pollutants and anthropogenic
disturbances in general (Hofmann, 1999). These same
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Corresponding author:
Elena Fabbri
Interdepartment Centre for Environmental Science
Research
University of Bologna, campus of Ravenna
via S. Alberto 163, 48100 Ravenna, Italy
E-mail:...