Abstract
The expression pattern of two major chaperones, the heat shock proteins (HSPs) HSP60 and HSP70 was studied in vitro in tissues of the housefly Musca domestica during larval and adult stages of development to identify their immunological relatives and understand their functional significance in normal cellular activities and during thermal stress. Fluorographs of labeled polypeptides and western blots demonstrated that both HSPs are expressed constitutively and heat-induced in all the larval and adult cell types examined. The pattern of whole tissue immunocytochemical staining using anti-HSP60 and anti-HSP70 antibodies corresponded well with the observations from western blots or fluorographs. In developing oocytes, both constitutive and heat inducible expression of HSP60 were regulated in an oocyte stage-specific manner. In unstressed ovaries the expression of these proteins was less pronounced in early stage oocytes (1st - 8th) than at later stages (9th and onward). The heat shock, however, induced both HSP70 and HSP60 to a significantly high level in early stage oocytes (1st-8th) as compared to their respective controls. Our findings indicate the involvement of the HSP60 and HSP70 proteins in the development, growth and differentiation of both somatic and germ line tissues. Furthermore, the enhanced co-expression of HSP70 and HSP60 upon heat shock in various larval and adult cell types suggests the possible role of HSP60 in thermoprotection.
Highlights
Temperature plays a key role in the survival of an organism up to a certain threshold
The level of heat stress induction of HSP60 relative to controls appeared to vary in different tissues, being higher in salivary gland, fat body, hindgut and brain ganglia than in Malpighian tubules or midgut tissue
Western blotting for HSP70 showed a similar heat induced expression pattern in that the response was tissue-specific. The level of this heat shock protein was higher in brain and hindgut than in the other tissues (Figure 1C)
Summary
Temperature plays a key role in the survival of an organism up to a certain threshold. Possess a cellular mechanism to safeguard it from the injurious effect of heat stress through a unique class of proteins, the molecular chaperones or heat shock proteins (HSPs) (Feder and Hofmann 1998; Morimoto et al, 1994; Kregel 2002; Sorensen et al, 2003). Temperature is a major limiting factor for survival of small ectotherms, such as the flies, as they often remain exposed to extreme thermal variations in their natural habitat, during summer months. Under such conditions they are expected to be highly susceptible to heat induced injuries. At higher or lethal temperatures (46 °C to 48 °C) the percent survival and the level of expression of induced proteins decreased considerably
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