Comparative immunochemical and structural similarities of five stress proteins from various tissue types

P53 synthesis and phosphorylation in the aging diet-restricted rat following retinoic acid administration

Multiple doses of retinoic acid (RA) were administered intraperitoneally to three groups of male Fischer 344 rats over a 36 h period. The p53 isoforms from bone marrow nuclei in these three groups of rats were analyzed over time by two-dimensional polyacrylamide gel electrophoresis (PAGE) and fluorography for the incorporation of [35S]methionine (p53-synthesis) and [32P]phosphate (p53-phosphorylation). Two groups of rats, young (3.5 months) ad libitum (Y/AL) and old (28 months) ad libitum (O/AL), had free access to Purina rat chow; a third group of old (28 months) diet-restricted rats (O/DR) were maintained on a restricted caloric intake (60% of the AL diet) from 3 months of age. After 36 h of RA dosing, the PAGE patterns of p53 synthesis and phosphorylation in Y/AL and O/DR rats were very similar. In both groups, an increase in complexity was observed with labeling of additional isotypes possessing more acidic isoelectric values. In contrast, the O/AL animals showed a pattern of p53 isoform synthesis and phosphorylation that was considerably less complex and lacked the pronounced shift to more acidic forms following RA dosing. The p53 isoforms of O/AL rats as recognized by wild type (wt) Pab 246 antibody, were also much less dramatic in their increase to more acidic forms. Two-dimensional phospho-tryptic maps of Y/AL and O/DR rats were also very similar, both exhibiting two additional minor 32P-labeled fragments after RA dosing. The maps of O/AL rats did not show the two additional fragments following RA administration. After RA dosing, cyclin protein inhibitors (p16, p21, p27) revealed robust labeling with their respective antibodies in Y/AL and O/DR rats as analyzed by Western blotting. The O/AL animals showed marginally detectable antibody recognition of the cyclin inhibitors after RA dosing. Taken together, these data suggest that the biosynthesis and phosphorylation of p53 isoforms and the expression of cyclin dependent kinase inhibitor proteins is not significantly different between Y/AL and O/DR rats. Further, these results confirm and extend our previous observations that chronic diet-restriction attenuates the age related decline in the metabolic activity of nuclear protein products.

A nuclear protein associated with lethal heat shock of HL-60 cells

The responses to stress in living cells are well known. Thermal stress causes decreased protein synthesis as well as rapid induction of heat shock proteins (hsps), or alternately termed stress proteins (sps). The exposure of cultured promyelocytic leukemia cells (HL-60) to a 45 degrees C lethal heat shock for 1 h elicited synthesis and phosphorylation of a polypeptide M(r) 48,000 and pI 7.5 (p 48) as visualized by two-dimensional polyacrylamide gel ultra-microelectrophoresis. p 48, which was not observed at sublethal temperatures (39 and 41 degrees C), was synthesized during all phases of the cell cycle but was phosphorylated only in G0 + G1 and S-phases. The appearance of p 48 was marked by a concomitant and reciprocal reduction in hsps or sps 70 and 90. Distinct protease V8 fragment maps of p 48, hsps 70 and 90 in conjunction with immunochemical determination indicated vast differences in their primary structures. These facts suggest that p 48 was not formed from coalesced breakdown products of hsps 70 or 90. Western blotting showed that p 48 possessed the same immunochemical determinants as two other proteins with the same molecular mass but different isoelectric points. In an association assay, p 48 was shown to bind with actins and hsp 90 from HL-60 nuclei.

Relationship between stress protein induction in rat kidney by mercuric chloride and nephrotoxicity

Adverse environmental stimuli increase the synthesis of a class of proteins referred to as stress proteins. The effect of mercuric chloride, a model nephrotoxin, on protein synthesis in male rat kidney has been evaluated. Renal slices from exposed rats were incubated with [35S]methionine for 1 hr and subjected to SDS-PAGE, after which 35S-labeled proteins were detected by autoradiography. Enhanced de novo synthesis of 70- and 90-kDa relative molecular mass (M(r)) proteins were detected 2 hr after exposure to 1 mg Hg/kg, with maximum activity occurring at 4-8 hr. By 16 hr postinjection, synthesis of these two proteins had decreased. Dose-related increases in synthesis of these proteins, and of a 110-kDa protein, were observed 4 hr after i.v. injection of 0.25, 0.5, and 1.0 mg Hg/kg, with concomitant inhibition of synthesis of proteins of M(r) 38 and 68 kDa. At a dose of 1 mg/kg, kidney proximal tubules exhibited progressive degenerative changes from 4 to 24 hr. A functional deficit, decreased uptake of [para-3H]aminohippurate into renal slices, was not observed until 16 hr after i.v. injection of 1 mg/kg. No significant histopathologic changes were observed in kidneys 4 hr after treatment with 0.25 or 0.5 mg Hg/kg, iv. No changes in liver protein synthesis were apparent until 16-24 hr, where an increase in the 70- and 90-kDa proteins was observed. A concomitant increase in plasma sorbitol dehydrogenase activity occurred at 16-24 hr; however, there was no histopathological evidence of liver injury. The 72-kDa inducible member of the 70-kDa stress protein family and the 88-kDa member of the 90-kDa protein family were detected by immunoblotting techniques using monoclonal antibodies. The data demonstrate that Hg induces alterations in the expression of renal gene products in vivo as evidenced by enhanced stress protein synthesis and inhibition of synthesis of constitutive proteins. These changes in renal protein synthesis preceded overt renal injury, occurring in the early stages of nephropathy. Altered patterns of stress protein synthesis appeared to be target organ specific. The data suggest that altered protein synthesis patterns may serve as biomarkers of renal injury.