Induction of Hsp22 (HspB8) by estrogen and the metalloestrogen cadmium in estrogen receptor– positive breast cancer cells

Abstract

Estrogen (E 2 ) plays a critical role in the etiology and progression of human breast cancer. The estrogenic response is complex and not completely understood, including in terms of the involved responsive genes. Here we show that Hsp22 (synonyms: HspB8, E2IG1, H11), a member of the small heat shock protein (sHSP) superfamily, was induced by E 2 in estrogen receptor-positive MCF-7 breast cancer cells, resulting in an elevated Hsp22 protein level, whereas it was not induced in estrogen receptor-negative MDA-MB-231 cells. This induction was prevented by the pure anti-estrogen ICI182780 (faslodex, fulvestrant), whereas tamoxifen, a substance with mixed estrogenic and antiestrogenic properties, had no major inhibitory effect on this induction, nor did it induce Hsp22 on its own. Cadmium (Cd) is an environmental pollutant with estrogenic properties (metalloestrogen) that has been implicated in breast cancer. Treatment of MCF-7 cells with Cd also resulted in induction of Hsp22, and this induction was also inhibited by ICI182780. In live MCF-7 cells, Hsp22 interacted at the level of dimers with Hsp27, a related sHSP, as was shown by quantitative fluorescence resonance energy transfer measurements. In cytosolic extracts of MCF-7 cells, most of the E 2 -and Cd-induced Hsp22 was incorporated into high-molecular mass complexes. In part, Hsp22 and Hsp27 were components of distinct populations of these complexes. Finally, candidate elements in the Hsp22 promoter were identified by sequence analysis that could account for the induction of Hsp22 by E 2 and Cd. Taken together, Hsp22 induction represents a new aspect of the estrogenic response with potential significance for the biology of estrogen receptorpositive breast cancer cells.

Structure and properties of chimeric small heat shock proteins containing yellow fluorescent protein attached to their C-terminal ends

“…Chimeras of HspB1, HspB5, HspB6, and HspB8 containing different fluorescent proteins (green, cyan, yellow, and citrine) fused to the N-terminal ends or to the C-terminal ends of sHsp were designed and successfully used in a number of investigations Abraham 2011, 2013;Borrelli et al 2002;Shelden et al 2002;Qian et al 2006;Fontaine et al 2005Fontaine et al , 2006Sun et al 2004Sun et al , 2007Doshi et al 2009). …”

“…Utilization of fluorescent proteins seems to be a very promising tool for this purpose (Chudakov et al 2010). A number of different fluorescent chimeras of sHsp have been designed and used for investigation of the intracellular location (Doshi et al 2009;Qian et al 2006;Borrelli et al 2002;Shelden et al 2002;Abraham 2011, 2013;Irobi et al 2004;Sun et al 2007) and formation of homooligomeric and heterooligomeric complexes of sHsp (Fontaine et al 2005;Fontaine et al 2006;Sun et al 2004;Datskevich et al 2012a). Utilization of fluorescent chimeras of sHsp has provided important and interesting information.…”

HSPB8 (heat shock 22kDa protein 8)

“…The mechanisms responsible for the cell type specificity of the HspB8 DNA methylation patterns are still unclear. Also unclear is the relationship between methylation and accessibility to expression regulatory factors, such as HSF or estrogen (Charpentier et al, 2000;Sun et al, 2007). HspB and co-variant genes in differentiation/development HspB8 is expressed in the adult mouse and rat hippocampus, but expression is modest or absent at the embryonic and postnatal stages (Kirbach and Golenhofen, 2011).…”

Abnormal interaction of motor neuropathy-associated mutant HspB8 (Hsp22) forms with the RNA helicase Ddx20 (gemin3)

“…The approximate positions of the marker proteins β-lactoglobulin B (∼5.1), phycocyanin (∼4.6), and glucose oxidase (∼4.2) are indicated HspB1, HspB2, HspB5, HspB6, and HspB7 (Sun et al 2004;Fontaine et al 2005), although oligomeric forms could not be detected using recombinant HspB8 (Chowdary et al 2004;Kim et al 2004). However, in extracts of cardiac and breast cancer cells, recruitment of HspB8 into highmolecular-mass material was reported, even though the nature of this material is not known (Fontaine et al 2005;Sun et al 2007). Association of HspB8 with other proteins may account for such high-molecular-mass species (see below).…”