Concurrent collapse of keratin filaments, aggregation of organelles, and inhibition of protein synthesis during the heat shock response in mammary epithelial cells.

Abstract

Abstract. The sequence of heat shock-induced perturbations in protein synthesis and cytoskeletal organization was investigated in primary cultures of mouse mammary epithelial cells (MMEC). Exposure of the cells to 45°C for 15 min caused a marked inhibition of protein synthesis through 2 h after heat. Resumption of protein synthesis began by 4 h, was complete by 8 h, and was accompanied by induction of four major heat shock proteins (HSPs) of 68, 70, 89, and 110 kD. Fluorescent cytochemistry studies indicated that heat shock elicited a reversible change in the organization of keratin filaments (KFs) and actin filaments but had a negligible effect on microtubules. Changes in the organization of KFs progressed gradually with maximal retraction and collapse into the perinuclear zone occurring at 1-2 h after heat followed by restoration to the fully extended state at 8 h. In contrast, actin illaments disappeared immediately after heat treatment and then rapidly returned within 30-60 min to their original appearance. The translocation of many organelles first into and then away from the juxtanuclear area along with the disruption and reformation of polyribosomes were concurrent with the sequential changes in distribution of KFs. The recovery of the arrangement of KFs coincided with but was independent of the resumption of protein synthesis and induction of HSPs. Thermotolerance could be induced in protein synthesis and KFs, but not in actin filaments, by a conditioning heat treatment. Neither protein synthesis nor induction of HSPs was necessary for the acquisition of thermotolerance in the KFs. The results are compatible with the possibility that protein synthesis may depend on the integrity of the KF network in MMEC. Heat shock thus can efficiently disarrange the KF system in a large population of epithelial cells, thereby facilitating studies on the functions of this cytoskeletal component.T HE effects of temperature elevation on cellular physiology have been studied in widely divergent organisms from bacteria to man (58). The dramatic changes in gene programming characterized by the induction of a specific set of proteins, usually referred to as heat shock proteins (HSPs),t together with inhibition in the synthesis of most other cellular proteins have been recognized as the main features of the heat shock response (43,51,61). This response is thought, at the simplest level, to be homeostatic to protect the cell against the environmental insult and provide it with the capacity to survive the crisis and preserve normal cellular activities. However, the molecular mechanisms responsible for these modifications remain obscure.Along with the rapid and transient reprogramming of transcription and translation, alterations in cellular morphology

Heat stress affects the organization of microtubules and cell division in Nicotiana tabacum cells

“…Reorganization of tnitotie spindle tnictotubules in animal cells exposed to elevated temperatures was demonsttated by means of electron microscopy (Rieder & Bajer 1977). Reanangement of the intetphase mictotubule network in response to heat stress has been observed in cytotoxic Tlymphocytes (Knox et al 1991), Neuro 2 A cells (Henegouwen & Linnemans 1987) and mouse epithelial cells (Shyy et al 1989). These findings may reflect a diffetence in sensitivity of higher plant and mammalian interphase microtubules to elevated temperatures, whilst the mitotic tnicrotubules in animals and plants are equally susceptible to heat stress.…”

Induction of rapid and reversible cytokeratin filament network remodeling by inhibition of tyrosine phosphatases

“…Granular aggregates are also a hallmark of various genodermatoses (Anton-Lamprecht, 1983;Coulombe et al, 1991;Cadrin and Martinoli, 1995;Kobayashi et al, 1999). Furthermore, granules are formed in vitro in response to temperature stress or to drugs that affect the state of cellular phosphorylation (Schliwa and Euteneuer, 1979;Shyy et al, 1989;Falconer and Yeung, 1992;Kasahara et al, 1993;Liao et al, 1995;Blankson et al, 1995;Toivola et al, 1997;Strnad et al, 2001). Elucidation of the mechanisms of granule formation may reveal ways to influence their formation and thereby positively affect disease outcome.…”

The Dynamic Duo of Small Heat Proteins and IFs Maintain Cell Homeostasis, Resist Cellular Stress and Enable Evolution in Cells and Tissues

“…Kelley and Schlesinger 1978 ), but taking the chicken embryo fi broblast as an example, vimentin was also robustly labeled with 35 S-methionine along with the resident small heat shock protein (Collier and Schlesinger 1986 ). Similar results were obtained in other cells expressing both protein chaperones and IF proteins (Vilaboa et al 1997 ;Slater et al 1981 ;Shyy et al 1989 ). Indeed, an interesting observation from these early studies was that preconditioning stresses helped protect the IF cytoskeleton against heatstress induced collapse (e.g.…”