Cell-specific expression of heat shock proteins in chicken reticulocytes and lymphocytes.

Abstract

We have found that chicken reticulocytes respond to elevated temperatures by the induction of only one heat shock protein, HSP70, whereas lymphocytes induce the synthesis of all four heat shock proteins (89,000 mol wt, HSP89; 70,000 tool wt, HSP70; 23,000 mol wt, HSP23; and 22,000 mol wt, HSP22). The synthesis of HSP70 in lymphocytes was rapidly induced by small increases in temperature (2°-3°C) and blocked by preincubation with actinomycin D. Proteins normally translated at control temperatures in reticulocytes or lymphocytes were not efficiently translated after incubation at elevated temperatures. The preferential translation of mRNAs that encode the heat shock proteins paralleled a block in the translation of other cellular proteins. This effect was most prominently observed in reticulocytes where heat shock almost completely repressed c~-and/3-globin synthesis.HSP70 is one of the major nonglobin proteins in chicken reticulocytes, present in the nonheat-shocked cell at approximately 3 x 106 molecules per cell. We compared HSP70 from normal and heat-shocked reticulocytes by two-dimensional gel electrophoresis and by digestion with Staphylococcus aureus V8 protease and found no detectable differences to suggest that the P70 in the normal cell is different from the heat shock-induced protein, HSP70. P70 separated by isoelectric focusing gel electrophoresis into two major protein spots, an acidic P70A (apparent pl = 5.95) and a basic P70B (apparent pl = 6.2). We observed a tissue-specific expression of P70A and P70B in lymphocytes and reticulocytes. In lymphocytes, P70A is the major 70,000-mol-wt protein synthesized at normal temperatures whereas only P70B is synthesized at normal temperatures in reticulocytes. Following incubation at elevated temperatures, the synthesis of both HSP70A and HSP70B was rapidly induced in lymphocytes, but synthesis of only HSP70B was induced in reticulocytes.Procaryotic and eucaryotic cells respond to elevated temperatures by the synthesis of the ubiquitous "heat shock" proteins, a family of proteins of 80-90,000 mol wt, 70,000 mol wt, and smaller proteins of 20-30,000 mol wt (36). Other cellular effects of heat shock include altered cell morphology (37, 40), inhibition of DNA synthesis affecting the cell cycle and mitosis (12, 34), a generalized repression in RNA polymerase ll-dependent transcription (10, 38), and the selective translation of heat shock messenger RNAs (23,25). Heat shock proteins are also induced in various cells after exposure to diverse and apparently unrelated chemicals including heavy metals (Cd, Cu, Zn), inhibitors of energy metabolism (arsenite), amino acid analogues (canavanine, 5-methyltryptophan), chelators (disulfiram), and infection with certain viruses such as adenovirus 5 (2, 15, 17, 21, 32).Among diverse organisms as yeast, Drosophila, chicken, mouse, and human, these induced proteins are highly conserved. Kelley et al. (18) have shown that heat shock proteins from different eucaryotes are antigenically related to the chicken heat shock pro...

Hemin-induced transcriptional activation of the HSP70 gene during erythroid maturation in K562 cells is due to a heat shock factor-mediated stress response.

“…In support of the first suggestion, there are several observations linking the expression of HSP70 with the process of erythroid maturation. In chicken reticulocytes, the HSP70 gene is constitutively transcribed (2) and the protein accumulates to high levels (16). Moreover, HSP70 is expressed in the primitive lineage of chicken embryonic erythrocytes (1).…”

“…For example, high levels of HSP70 are found in chicken reticulocytes (16). Moreover, HSP70 is constitutively expressed in primitive chicken embryonic erythrocytes (1) and is transcribed in adult reticulocytes in the absence of heat shock (2).…”

Chaperoning erythropoiesis

“…Approximately 20 years ago, several groups noted that the molecular chaperone Hsp70 accumulates to high levels in erythroid precursors. [1][2][3][4][5] Accordingly, investigators speculated that Hsp70 and related chaperones, proteins that regulate the folding, degradation, and activities of other proteins, might have specialized functions in streamlining erythroid maturation. 2 Molecular chaperones are defined as a diverse group of proteins that guide the folding and assembly of other proteins, but are not associated with the functional end product.…”

Control of red cell function of late chick embryos: role of extracellular ATP/AMP and egg size

“…Whereas the gene expression of S17, ␤-globin, transferrin receptor, GATA-3, histone H5, heat-shock factor-3, and heme oxygenase-1 was unresponsive to cAMP (n Ն 2, data not shown), we identified the HSP70, one of the major nonglobin proteins in chicken reticulocytes (23), as a cAMP-responsive gene in definitive embryonic RBC. During a 4-h in vitro incubation of day 11 RBC, the hsp70 expression was increased significantly by either ␤-adrenergic or adenosine receptor activation with a similar time course of expression as observed for caII (Figs.…”