scholarly journals The intracellular location of yeast heat-shock protein 26 varies with metabolism.

1989 ◽  
Vol 108 (2) ◽  
pp. 425-439 ◽  
Author(s):  
J M Rossi ◽  
S Lindquist

An antibody highly specific for heat-shock protein (hsp)26, the unique small hsp of yeast, and mutants carrying a deletion of the HSP26 gene were used to examine the physical properties of the protein and to determine its intracellular distribution. The protein was found in complexes with a molecular mass of greater than 500 kD. Thus, it has all of the characteristics, including sequence homology and induction patterns, of small hsps from other organisms. When log-phase cells growing in glucose were heat shocked, hsp26 concentrated in nuclei and continued to concentrate in nuclei when these cells were returned to normal temperatures for recovery. However, hsp26 did not concentrate in nuclei under a variety of other conditions. For example, in early stationary-phase cells hsp26 is induced at normal growth temperatures. This protein was generally distributed throughout the cells, even after heat shock. Similarly, in cells genetically engineered to synthesize hsp26 in the presence of galactose, hsp26 did not concentrate in nuclei, with or without a heat shock. To determine if the failure of hsp26 to concentrate in the nucleus of these cells was due to the fact that the protein had been produced at 25 degrees C or to a difference in the physiological state of the cell, we investigated the distribution of the heat-induced protein in cells grown under several different conditions. In wild-type cells grown in galactose or acetate and in mitochondrial mutants grown in glucose or galactose, hsp26 also failed to concentrate in nuclei with a heat shock. We conclude that the intracellular location of hsp26 in yeast depends upon the physiological state of the cell and not simply upon the presence or absence of heat stress. Our findings may explain why previous investigations of the intracellular localization of small hsps in a variety of organisms have yielded seemingly contradictory results.

1992 ◽  
Vol 70 (12) ◽  
pp. 1347-1355 ◽  
Author(s):  
H. S. Roychowdhury ◽  
T. J. MacAlister ◽  
J. W. Costerton ◽  
M. Kapoor

The most abundant heat-shock protein of Neurospora crassa is a multimeric glycoprotein of 80-kilodaltons (i.e., HSP80), induced strongly by hyperthermia and at a lower level by sodium arsenite, ethanol, and carbon source depletion. Immunoelectron microscopy, using indirect immunogold labelling demonstrated that HSP80 was undetectable in mycelium cultured at the normal growth temperature of 28 °C, but it appeared rapidly following the commencement of heat-shock treatment at 48 °C. HSP80, visualized by the gold label, was observed almost exclusively in the cytoplasm, exhibiting a uniform distribution. Association of this protein with cellular membranes and (or) targeting to a particular subcellular compartment or organelle was not apparent.Key words: 80-kilodalton heat-shock protein, Neurospora, intracellular location, immunoelectron microscopy.


1989 ◽  
Vol 9 (6) ◽  
pp. 2615-2626 ◽  
Author(s):  
E Hickey ◽  
S E Brandon ◽  
G Smale ◽  
D Lloyd ◽  
L A Weber

Vertebrate cells synthesize two forms of the 82- to 90-kilodalton heat shock protein that are encoded by distinct gene families. In HeLa cells, both proteins (hsp89 alpha and hsp89 beta) are abundant under normal growth conditions and are synthesized at increased rates in response to heat stress. Only the larger form, hsp89 alpha, is induced by the adenovirus E1A gene product (M. C. Simon, K. Kitchener, H. T. Kao, E. Hickey, L. Weber, R. Voellmy, N. Heintz, and J. R. Nevins, Mol. Cell. Biol. 7:2884-2890, 1987). We have isolated a human hsp89 alpha gene that shows complete sequence identity with heat- and E1A-inducible cDNA used as a hybridization probe. The 5'-flanking region contained overlapping and inverted consensus heat shock control elements that can confer heat-inducible expression on a beta-globin reporter gene. The gene contained 10 intervening sequences. The first intron was located adjacent to the translation start codon, an arrangement also found in the Drosophila hsp82 gene. The spliced mRNA sequence contained a single open reading frame encoding an 84,564-dalton polypeptide showing high homology with the hsp82 to hsp90 proteins of other organisms. The deduced hsp89 alpha protein sequence differed from the human hsp89 beta sequence reported elsewhere (N. F. Rebbe, J. Ware, R. M. Bertina, P. Modrich, and D. W. Stafford (Gene 53:235-245, 1987) in at least 99 out of the 732 amino acids. Transcription of the hsp89 alpha gene was induced by serum during normal cell growth, but expression did not appear to be restricted to a particular stage of the cell cycle. hsp89 alpha mRNA was considerably more stable than the mRNA encoding hsp70, which can account for the higher constitutive rate of hsp89 synthesis in unstressed cells.


2001 ◽  
Vol 6 (1) ◽  
pp. 59 ◽  
Author(s):  
Peter J. Mark ◽  
Bryan K. Ward ◽  
Premlata Kumar ◽  
Hooshang Lahooti ◽  
Rodney F. Minchin ◽  
...  

1990 ◽  
Vol 10 (10) ◽  
pp. 5160-5165
Author(s):  
S Ahmad ◽  
R Ahuja ◽  
T J Venner ◽  
R S Gupta

A major cellular protein (P2; approximately 70 kilodaltons) which is altered in Chinese hamster ovary (CHO) cell mutants resistant to the microtubule inhibitors colchicine and podophyllotoxin has been shown to correspond to the constitutive form of the 70-kilodalton heat shock protein (hsc70). The inference that P2 and hsc70 are the same protein is based on the following observations: (i) migration of P2 in two-dimensional polyacrylamide gels in the same position as that reported for hsc70; (ii) cross-reactivity of a monoclonal antibody which reacts with both the constitutive and induced forms of hsp70 with the P2 spot from wild-type CHO cells and with both P2 and a mutant form of P2 in a CHO cell mutant; (iii) specific reactivity of a polyclonal antibody to P2 with both the constitutive and heat-induced forms of hsp70 in human cells; (iv) identical immunofluorescent staining of dot/patchlike structures with both P2 and hsp70 antibodies in human and CHO cells; and (v) a cDNA clone for hsc70 has been isolated and sequenced from wild-type CHO cells. The in vitro transcription and translation product of this cDNA has been shown to comigrate with the P2 protein spot in two-dimensional gels, indicating their identity. The fact that there is an alteration in hsc70 in mutants resistant to antimitotic drugs suggests a role for this protein in the in vivo assembly and function of microtubules.


Cells ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1263 ◽  
Author(s):  
Maxim Shevtsov ◽  
Zsolt Balogi ◽  
William Khachatryan ◽  
Huile Gao ◽  
László Vígh ◽  
...  

Heat shock proteins (HSPs) constitute a large family of conserved proteins acting as molecular chaperones that play a key role in intracellular protein homeostasis, regulation of apoptosis, and protection from various stress factors (including hypoxia, thermal stress, oxidative stress). Apart from their intracellular localization, members of different HSP families such as small HSPs, HSP40, HSP60, HSP70 and HSP90 have been found to be localized on the plasma membrane of malignantly transformed cells. In the current article, the role of membrane-associated molecular chaperones in normal and tumor cells is comprehensively reviewed with implications of these proteins as plausible targets for cancer therapy and diagnostics.


1990 ◽  
Vol 87 (2) ◽  
pp. 846-850 ◽  
Author(s):  
J. Fargnoli ◽  
T. Kunisada ◽  
A. J. Fornace ◽  
E. L. Schneider ◽  
N. J. Holbrook

2011 ◽  
Vol 300 (3) ◽  
pp. C636-C646 ◽  
Author(s):  
Grazia Tamma ◽  
Joris H. Robben ◽  
Christiane Trimpert ◽  
Michelle Boone ◽  
Peter M. T. Deen

Vasopressin-induced water reabsorption coincides with phosphorylation of aquaporin-2 (AQP2) at S256 (pS256), dephosphorylation at S261, and its translocation to the apical membrane, whereas treatment with the phorbol ester 12-tetradecanoylphorbol-13-acetate (TPA) induces AQP2 ubiquitination at K270, its internalization, and lysosomal degradation. In this study we investigated the relationship between S256 and S261 phosphorylation in AQP2 and its ubiquitination and trafficking in MDCK cells. Forskolin stimulation associated with increased pS256 and decreased pS261 AQP2, indicating that MDCK cells are a good model. After forskolin stimulation, TPA-induced ubiquitination of AQP2 preceded phosphorylation of AQP2 at S261, which in the first instance occurred predominantly on ubiquitinated AQP2. Forskolin-induced changes in pS261 were also observed for AQP2-S256A and AQP2-S256D, which constitutively localize in vesicles and the apical membrane, respectively. Although pS261 varies with forskolin as with wild-type AQP2, AQP2-S256A is not increased in its ubiquitination. Our data reveal that pS261 occurred independently of AQP2 localization and suggest that pS261 follows ubiquitination and endocytosis and may stabilize AQP2 ubiquitination and intracellular localization. The absence of increased ubiquitination of AQP2-S256A indicates that its intracellular location is due to the lack of pS256. Furthermore, AQP2-S261A and AQP2-S261D localized to vesicles, which was due to their increased ubiquitination, because changing K270 into Arg in both mutants resulted in their localization in the apical membrane. Although still increased in its ubiquitination, AQP2-S256D-S261D localized in the apical membrane. AQP2-S256D-K270R-Ub, however, localized to intracellular vesicles. Although our localization of AQP2-S261A/D is different from that of others, these data indicate that constitutive S256 phosphorylation counterbalances S261D-induced ubiquitination and internalization or changes its structure to allow distribution to the apical membrane. The vesicular localization of AQP2-S256D-K270R-Ub, however, indicates that the dominant apical sorting of S256D can again be overruled by constitutive ubiquitination. These data indicate that the membrane localization of AQP2 is determined by the balance of the extents of phosphorylation and ubiquitination.


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