Dynamic changes in intracellular localization and isoforms of the 27-kD stress protein in human keratinocytes

Expression of the 27-kDa heat shock protein in human epidermis and in epidermal neoplasms: an immunohistological study

The 27-kDa heat shock protein (HSP27) is a member of the small heat shock protein (HSP) family. In addition to its putative function in thermotolerance, this protein may play a part in the regulation of cell growth and differentiation. This study was conducted to assess the significance of the expression of HSP27 in human epidermis and in cutaneous neoplasms. Sixty-two biopsy samples from normal human skin and from inflammatory and neoplastic skin diseases were investigated by immunohistochemistry on formalin-fixed paraffin-embedded tissue sections, using a monoclonal antibody specific for HSP27. In normal human epidermis, HSP27 is expressed in the upper epidermal layers with a cytoplasmic staining pattern. The basal cell layer does not express detectable amounts of HSP27. In hair follicles, staining is mainly confined to the outer root sheath and to the infundibular epithelium. Melanocytes, dermal fibroblasts and endothelial cells do not express detectable amounts of HSP27. HSP27 could not be detected in fetal skin until the 20th week of gestation. Tumour cells in basal and squamous cell carcinomas do not express significant amounts of HSP27. In solar keratoses, seborrhoeic keratoses, human papillomavirus (HPV)-induced hyperproliferative lesions and inflammatory skin conditions, HSP27 expression largely resembles the pattern observed in normal human skin. HSP27 is expressed in a differentiation-related pattern in normal human epidermis and hyperproliferative disorders of the epidermis. We conclude that HSP27 may be regarded as a marker of differentiation in epidermal keratinocytes. Absence of HSP27 in the upper epidermal layers may be a marker for epidermal malignancy.

Heat shock proteins and molecular chaperones: implications for adaptive responses in the skin

Recent advances in the biology of heat-shock proteins (hsps) are reviewed. These abundant and evolutionarily highly conserved proteins (also called stress proteins) act as molecular escorts. Hsps bind to other cellular proteins, help them to fold into their correct secondary structures, and prevent misfolding and aggregation during stress. Cytoplasmic hsp70 and hsp60 participate in complicated protein-folding pathways during the synthesis of new polypeptides. Close relatives of hsp70 and hsp60 assist in the transport and assembly of proteins inside intracellular organelles. Hsp90 may have a unique role, binding to the glucocorticoid receptor in a manner essential for proper steroid hormone action. Hsps may also be essential for thermotolerance and for prevention and repair of damage caused by ultraviolet B light. A unique class of T lymphocytes, the gamma delta T cells, exhibits a restricted specificity against hsps. These T cells may constitute a general, nonspecific immune mechanism directed against the hsps within invading organisms or against very similar hsps within invading organisms or against very similar hsps expressed by infected (stressed) keratinocytes. Immunologic cross-reactivity between hsps of foreign organisms and of the host may play a role in some autoimmune diseases. Although hsps are expressed in the skin, many questions remain about their role during injury, infection, and other types of cutaneous pathophysiology.