Proliferation, migration, and resistance to oxidative and thermal stresses of HT1080 cells with knocked out genes encoding Hsp90α and Hsp90β

Heat shock protein 90 (Hsp90) fulfils essential housekeeping functions in the cell associated with the folding, stabilization, and turnover of various proteins. In mammals, there exist two Hsp90 isoforms, stress-inducible Hsp90α and constitutively expressed Hsp90β. In an attempt to identify cellular processes dependent on Hsp90α and Hsp90β, we generated a panel of clones of human fibrosarcoma HT1080 cells with the knocked out HSP90AA1 or HSP90AB1 genes encoding, respectively, Hsp90α and Hsp90β. The knockout of the HSP90AA1 and HSP90AB1 genes practically did not affect cell proliferation and resistance to thermal shock and oxidative stress. The loss of Hsp90α in Hsp90α-null cell clones also did not impair cell migration, while the migration of the Hsp90β-null cell clones was prominently reduced as compared to parent HT1080 cells. This indicated the necessity of Hsp90β for efficient basal migration of HT1080 cells whereas Hsp90α seems to be dispensable for this process. The knockout of one Hsp90 isoform was invariably accompanied by an increase in the level of the other Hsp90 isoform by 30-50%, which partly or fully compensated for a decrease in the total level of Hsp90. Thus, we demonstrated the dispensability of Hsp90α and Hsp90β for HT1080 cells in several cellular processes under normal and stress conditions, which suggested the participation of the two Hsp90 isoforms in the same biological processes and full or at least partial functional substitution of one Hsp90 isoform by the other.

A 2,5-Dihydroxybenzoic Acid-Gelatin Conjugate: The Synthesis, Antiviral Activity and Mechanism of Antiviral Action Against Two Alphaherpesviruses

Various natural and synthetic polyanionic polymers with different chemical structures are known to exhibit potent antiviral activity in vitro toward a variety of enveloped viruses and may be considered as promising therapeutic agents. A water-soluble conjugate of 2,5-dihydroxybezoic acid (2,5-DHBA) with gelatin was synthesized by laccase-catalyzed oxidation of 2,5-DHBA in the presence of gelatin, and its antiviral activity against pseudorabies virus (PRV) and bovine herpesvirus type 1 (BoHV-1), two members of the Alphaherpesvirinae subfamily, was studied. The conjugate produced no direct cytotoxic effect on cells, and did not inhibit cell growth at concentrations up to 1000 µg/mL. It exhibited potent antiviral activity against PRV (IC50, 1.5-15 µg/mL for different virus strains) and BoHV-1 (IC50, 0.5-0.7 µg/mL). When present during virus adsorption, the conjugate strongly inhibited the attachment of PRV and BoHV-1 to cells. The 2,5-DHBA-gelatin conjugate had no direct virucidal effect on the viruses and did not influence their penetration into cells, cell-to-cell spread, production of infectious virus particles in cells, and expression of PRV glycoproteins E and B. The results indicated that the 2,5-DHBA-gelatin conjugate strongly inhibits the adsorption of alphaherpesviruses to cells and can be a promising synthetic polymer for the development of antiviral formulations against alphaherpesvirus infections.

Release of the glucose-regulated protein 94 by baby hamster kidney cells

Glucose-regulated protein 94 (grp94) is a major component of the endoplasmic reticulum (ER) lumen of eukaryotic cells. We showed that grp94 is released from baby hamster kidney (BHK-21) cells into a serum-free medium. The exit of grp94 into the medium was not related to the protein discharge due to cell death and was independent of de novo protein synthesis. The treatment of cells with brefeldin A and monensin, the inhibitors of the classical pathway of protein secretion, did not decrease the extracellular level of grp94, indicating that the discharge of grp94 from cells does not occur through the ER/Golgi-dependent pathway. Exosomes, membrane vesicles secreted by several cell types, were not involved in the release of grp94 from cells. Methyl-β-cyclodextrin, a substance that disrupts the lipid raft organization, considerably reduced the extracellular level of grp94, indicating that lipid rafts are involved in the liberation of grp94 from BHK-21 cells. The results suggest that BHK-21 cells release grp94 into the serum-free medium via the nonclassical secretory pathway in which lipid rafts play an important role.

Purification of the 90 kDa heat shock protein (hsp90) and simultaneous purification of hsp70/hsc70, hsp90 and hsp96 from mammalian tissues and cells using thiophilic interaction chromatography

Heat shock proteins (HSPs) hsp70/hsc70, hsp90 and hsp96 were separated from mammalian cells and tissues on a gel obtained by the reaction of beta-mercaptoethanol with divinyl sulfone-activated Sepharose CL-6B (thiophilic gel or T-gel). Hsp90 revealed a much higher affinity towards the T-gel than the other HSPs. One-step thiophilic interaction chromatography of proteins resulted in a more than 80% purity and 85% yield of hsp90. Based on this observation, a simple and efficient method for the purification of hsp90 and a procedure for the simultaneous purification of several HSPs (hsp70/hsc70, hsp90 and hsp96) using thiophilic interaction chromatography was developed. All the HSPs were recovered with a high yield and purity (90-99%). The results indicated that the thiophilic gel is a highly efficient affinity matrix for the purification of hsp90 and can be used in the protocols of purification of different HSPs from cells and tissues of various animal species.