Superinduction by cycloheximide of mitogen‐induced secreted proteins produced by Balb/c 3T3 cells

Abstract

We describe here some of the characteristics of the regulation of a group of secretory proteins whose secreted levels rise within 2-4 h of adding fibroblast growth factor (FGF), epidermal growth factor (EGF), or serum to quiescent Balb/c 3T3 cells. The levels of these secretory proteins are regulated similarly to the interferons. When cycloheximide is present during the induction period, the amounts of [35S]methionine incorporated into five of these proteins that we have called "superinducible proteins" (SIPs) is increased 2-5-fold. Superinduction of the SIPs is seen also in response to polyribol-polyriboC, the classical inducer of interferons. None of the SIPs, however, are immuno-precipitated by anti-beta-interferon antibody. Induction and superinduction of the SIPs is inhibited by actinomycin D. Superinduction occurs at concentrations of cycloheximide that inhibit protein synthesis by at least 85%. The SIPs are not major intracellular proteins; they are barely detectable in cellular fractions. Their induction is, however, correlated with the ability of the polypeptide growth factor to stimulate DNA synthesis; EGF, FGF, and serum induce the SIPs, whereas insulin does not, and insulin alone weakly stimulates DNA synthesis in these cells. Because FGF, EGF, and serum cause the SIPs to be produced at concentrations of cycloheximide that inhibit 85% of bulk protein and DNA synthesis, it follows that the SIPs are produced directly from the action of the growth factor and not as a consequence of increased growth. Although probably not interferons, in analogy to the lymphokines, the SIPs could be a set of autocrine or paracrine factors that rapidly convey the growth or differentiation signal between cells.

Identification of a New Acute Phase Protein

“…The cells were then metabolically labeled for 4 h by incubation with 100 mCi/ml Tran 35 S-label in DME (with 10% of the normal methionine concentration), 0.2% calf serum, and the same additions as present during the previous 24-h incubation. Details of this procedure have been described (7)(8)(9)15). The samples of medium were resolved by SDS-PAGE, and the gels were impregnated with 2,5-diphenyloxazole and exposed to film.…”

“…We have reported previously the induction, characterization, purification, and partial peptide sequencing of a superinducible protein, SIP24, produced by quiescent Balb/c 3T3 mouse fibroblast cells (7)(8)(9). SIP24 is a 24-kDa secreted glycoprotein induced by serum, basic fibroblast growth factor (bFGF), prostaglandin F2␣ (PGF2␣), phorbol ester, and dexamethasone.…”

A Dual Role of Lipocalin 2 in the Apoptosis and Deramification of Activated Microglia

“…LCN2 is also known as 24p3 (24), 24-kDa superinducible protein (SIP24) (25), and neutrophil gelatinase-associated lipocalin (NGAL; a human homolog of lcn2) (26,27). LCN2 has diverse functions.…”

A novel mechanism of resistance to α‐difluoromethylornithine induced by cycloheximide

“…DFMOresistant cells can also be obtained using the same CHM/DFMO treatment with the normal [24,25], superinduction of c-myc mRNA [26,27] and a transient reversion of the tumoral phenotype in viral and chemically transformed cells [28]. The mechanism by which DFMO-resistant cells were produced in our case does not involve gene amplification, the appearance of a DFMO-insensitive ODC, nor a decreased transport of DFMO.…”