DYNAMIC CHANGES IN INTRACELLULAR-LOCALIZATION AND ISOFORMS OF THE 27-KD STRESS PROTEIN IN HUMAN KERATINOCYTES

We have begun to characterize the low molecular weight, 27-kD heat sho ck or stress protein (HSP27) in normal keratinocytes and in HaCaT, a s pontaneously transformed keratinocyte line. The presence and location of HSP27 was determined by indirect immunofluorescence on fixed whole cells and immunoblot analysis of cytosolic, membrane, nuclear, and cyt oskeletal cell fractions. HSP27 is localized throughout the cytoplasm of cells at 37-degrees-C. After heating at 42-degrees-C, there is a ra pid (within 10 min) increase in nuclear HSP27. Two-dimensional gel ana lysis of whole cell HaCaT lysates identified multiple isoforms of HSP2 7 with different isoelectric points. The function of HSP27 is largely unknown but its presence throughout the cytoplasm of cells at 37-degre es-C, its translocation to the nucleus after cellular stress, and the presence of multiple isoforms suggest a biologic role in both stressed and unstressed human keratinocytes.