Heat shock proteins (HSPs), also called stress proteins, are not only induced
in response to elevated temperatures, but also as a result of various stress
situations, including environmental strains, viral infection, ischemia, anoxia
and oxidative stress. These stress situations trigger cellular defence mechanisms
that act as an emergency system capable of combatting the toxic consequences
due to the accumulation of misfolded proteins.
Heat shock proteins are involved in many physiological processes, including
development and differentiation, organisation of the cytoarchitecture by binding
to cytoskeletal elements and regulation of the balance between cell death and
survival. Many heat shock proteins work as molecular chaperones. In this role,
they contribute to in vivo protein folding and prevent nonproductive interactions
with other proteins and cellular components. In recent years it has been found
that the chaperone system and the proteolytic machinery work closely together,
and that proteasomal inhibition causes the upregulation of stress proteins.
Impairment of the proteasomal machinery and chaperone functions lead to protein
damage, which contributes to neurodegenerative disorders and to the aging process.
The brain is the most sensitive target for traumatic events. Many disorders
of the nervous system are caused by intracellular or extracellular deposits
of protein aggregates. Stress responses in the brain, as monitored by the induction
of heat shock proteins, occur in distinct regions and affect nerve cells and
glia in a cell-type-specific manner. Hence, stress proteins may serve as biomarkers
and provide diagnostic tools that allow us to identify stress specificity and
localize pathological processes. Their critical involvement during neurodegeneration
in brain disorders, such as Alzheimer’s, Parkinson’s and Huntington’s
diseases, and multiple sclerosis, makes them promising candidates for therapeutic
intervention and drug development.