Spleen cell phosphorylation of salt soluble nuclear protein from isoproterenol treated and sorted nuclei

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.

Comparison of the cell cycle regulated synthesis and phosphorylation of stress proteins, actin isoforms and a novel actin-like protein following drug administration in cultured rat lymphocytes

Administration of phytohemagglutinin initiated cycling of rat lymphocytes in vitro, and following treatment with this drug and other drugs in combination, lymphocytes were pulse labeled with [3H] leucine of [32P] phosphate. The nuclei were isolated from lymphocytes and collected from partitions of the cell cycle, and the proteins analyzed from fluorographs following gel electrophoresis for protein biomarkers after drug exposure. Stress proteins (sps) were dependent on a specific drug or drugs in combination (i.e., interleukin-2, bleomycin) for their synthesis that occurred only during the G1-phase of the cell cycle. An "actin-like" protein (A4) with electrophoretic mobilities similar to the actin complex, was synthesized in S and G2 phases and phosphorylated in all phases of the cell cycle only following the administration of drugs in combination. A4 exhibited a binding affinity for sp 24 that was cell cycle regulated (i.e., A4 from S phase did not bind with sp 24, but A4 from G2 phase did bind with the sp. Protein A4 appeared similar in some structural aspects to the nonmuscular actin isoform family but differed in epitope, suggesting a unique relationship and represented a stable protein, perhaps a product from the mutation of an actin gene. The dependence of certain sps and protein A4 for their induction by drugs in combination may serve as biomarkers of chemical interaction and toxicity.

The homology of a novel polypeptide with stress protein characteristics in embryonic mice brain and in the hypothalamus of caloric restricted rats as determined by ultramicro western blotting

A novel protein (p34) was observed in polyacrylamide gel fluorographs of gestation day 13 embryonic mouse brain following retinoic acid dosing of dams. Another p34 polypeptide with identical gel migratory characteristics was seen in the hypothalamus of old caloric restricted rats after "food deprivation stress". Western blotting, employing an ultramicro trans-blot cell developed in our laboratory, detected identical immunochemical determinants between these proteins, verifying their homology. Peptide mapping and Western blotting further validated the uniqueness of p34 compared with other stress proteins including heme oxygenase.

The temporal relationships of synthesis and phosphorylation in stress proteins 70 and 90 in aged caloric restricted rats exposed to bleomycin

A single intraperitoneal injection of the human therapeutic drug bleomycin (BL) was administered to three groups of male Fischer 344 rats at time 0, and the incorporation of [35S]methionine ("synthesis") and phosphorylation patterns of stress proteins (sps/hsps) from bone marrow cells were analyzed over time by two-dimensional electrophoresis and fluorography. Two groups of rats, young ad libitum (Y/AL--3 months) and old ad libitum (O/AL--28 months), had free access to rat chow, and a third group of old rats (O/CR--28 months) were maintained on a caloric restricted intake (60% of the AL diet). The administration of BL in Y/AL, O/AL and O/CR animals activated the 35S-labeling of sp 90 which reached a peak at 4 hours. Labeling of sp 90 was significantly greater in Y/AL compared to O/AL, and the incorporation pattern of O/CR was intermediate to Y/AL and O/AL animals. All labeling of sp 90 in each group had disappeared by 10 hours after BL administration. Stress protein 70x (inducible form) in these three animal groups displayed a similar pattern of 35S-incorporation, but the amount of labeling was less than that of sp 90. No labeling of sp 70x remained by 13 hours after BL administration. Phosphorylation ([32P] phosphate incorporation) of sp 90 reached a maximum level at 2 hours in all animals, and 32P-labeling in Y/AL was significantly increased over O/AL and O/CR with an intermediate level found in O/CR animals. The turnover rate (phosphorylation/dephosphorylation) of sp 90 induced by BL was significantly suppressed and temporarily extended in O/AL as compared with O/CR, which implied that CR not only increased incorporation of sp 90, but also enhanced a utilization of the phosphate pool very similar to that seen in Y/AL animals.

Comparative studies of synthesis, phosphorylation, DNA binding and proteolytic characteristics of a novel protein during phases of the mouse spleen cell cycle

1. Cultured mouse spleen cells were exposed to the mitogen Concanavalin A followed by isoproterenol, and nuclei were electronically sorted from seven partitions of the cell cycle. 2. Several nuclear proteins, including stress proteins, which were cell-cycle-stage specific, were elicited by isoproterenol as determined by micro-electrophoresis and fluorography. 3. Two novel S-phase proteins (X0 and X') demonstrated differing synthesis and phosphorylation patterns during the cell-cycle phases. 4. X' showed DNA binding characteristics and proteolytic properties (hydrolyzing X0 or beta-galactosidase); both proteins were cell-cycle regulated.

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.

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

1. Incorporation of radioactive phosphate or leucine by stress proteins from rodent lymphoma, submaxillary and liver nuclei were observed in two-dimensional gels following chemical and environmental stress. 2. The stress proteins were isolated from second-dimension gels and their similarities compared. Mol. wt determinations, immunochemical blotting and protease V8 peptide mapping confirmed the identical nature of the stress proteins possessing identical Mr, but from diverse tissue types. 3. These data imply that highly similar stress proteins exist in diverse tissues, are conserved during evolution, and possess some elemental and essential function.

Retinoic acid induction of stress proteins in fetal mouse limb buds

Retinoic acid (RA) is teratogenic in rodent embryos. Several teratogens have been shown to induce the synthesis of a subset of heat shock proteins (stress proteins) in Drosophila. To determine if RA induces the synthesis of these proteins in rodent embryos, pregnant ICR mice were dosed with 100 mg/kg RA on Day 11 of gestation. Forelimb buds were removed from embryos 2.5 hr post-RA-treatment and nuclei were isolated, stained, and sorted from stages of the cell cycle. Nuclear proteins were extracted and analyzed by two-dimensional polyacrylamide gel electrophoresis. Nuclear proteins with molecular weights of approximately 84 and 25 kDa were synthesized in embryos in the G0 + G1 phase after pregnant dams were treated with RA. Isoelectric points, molecular weights, immunochemical blotting, and polypeptide mapping demonstrated that these proteins are indistinguishable from stress proteins isolated under a variety of conditions from rat submaxillary glands and mouse lymphoma cells. These results suggest that treatment with RA induces the synthesis of a subset of stress proteins; the role of these proteins in the teratogenic effects of RA is not known.