title: Changes in cell morphology and actin organization during heat shock in Dictyostelium discoideum: does HSP70 play a role in acquired thermotolerance?
abstract: In response to heat shock (34 degrees C, 30 min), cell morphology and actin organization in Dictyostelium discoideum are drastically changed. Loss of pseudopodia and disappearance of F-actin-containing structures were observed by using fluorescence microscopy. These changes were paralleled by a rapid decrease of the F-actin content measured by a TRITC-phalloidin binding assay. The effects of heat shock on cell morphology and actin organization are transient: After heat shock (34 degrees C) or during a long-term heat treatment (30 degrees C), cell morphology, F-actin patterns and F-actin content recovered/adapted to a state which is characteristic for untreated cells. Because F-actin may be stabilized by increased amounts of heat shock proteins, their response and interaction with F-actin was analyzed. After a 1 h heat treatment (34 degrees C), the major heat shock protein of D. discoideum (HSP70) showed maximally increased synthesis rates and levels. During recovery from a 34 degrees C shock or during a continuous heat treatment at 30 degrees C, the HSP70 content first increased and then declined slowly toward normal levels. Pre-treatment of cells with a short heat shock of 30 min at 34 degrees C stabilized the F-actin content when the cells were exposed to a second heat shock. Furthermore, a transient colocalization of HSP70 and actin was observed at the beginning of heat treatment (30 degrees C) using immunological detection of HSP70 in the cytoskeletal actin fraction.
authors.affiliation: Institute of Cell Biology, Biochemistry and Biotechnology, University of Bremen, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Xiang
authors.forename: L
authors.initials: L
authors.lastname: Rensing
mesh_terms: D000199:Actins / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D004023:Dictyostelium / Q000378:metabolism / Q000502:physiology*; D018840:HSP70 Heat-Shock Proteins / Q000032:analysis / Q000502:physiology*; D006358:Hot Temperature; D008856:Microscopy, Fluorescence; D013997:Time Factors
chemical_list: D000199:Actins; D018840:HSP70 Heat-Shock Proteins