Yellow fever virus proteins NS2A, NS2B, and NS4B: identification and partial N-terminal amino acid sequence analysis

A series of fusion proteins corresponding to the hydrophobic ns2 and ns4 regions of yellow fever virus (YF) were generated in Escherichia coli using trpE fusion vectors. Antisera to ns2 and ns4 region fusion proteins recognize virus-specific proteins of 15 and 27 kDa, respectively. N-terminal amino acid sequence analysis of the 27-kDa protein indicates that the N-terminus of YF NS4B immediately follows a signalase-like cleavage site. Additional sequence data generated by microsequence analysis of labeled proteins immunoprecipitated with mouse hyperimmune antisera have identified the 15-kDa protein as NS2B and an additional 20-kDa viral protein as NS2A. Comparison of the sequences adjacent to the N-termini of these viral proteins suggests that three distinct types of cleavage events are involved in processing the hydrophobic YF ns2 and ns4 regions. These include cleavage after a short side chain amino acid to generate the N-terminus of NS2A, cleavage after two arginine residues to produce the N-terminus of NS2B, and a cleavage site consistent with the specificity of signalase to generate the N-terminus of NS4B. Analysis of virus-specific protein patterns in several different mammalian cell lines and in Aedes albopictus cells suggests that the same cleavage sites are used in different hosts. These findings are discussed in relation to the processing of flavivirus polyproteins.

Expression of nuclear lamins in mammalian somatic cells lacking cytoplasmic intermediate filament proteins

Using immunofluorescence and immunoblotting techniques, we have examined the composition of the nuclear lamina in murine plasmacytoma cells, MPC-11, exposed to the phorbol ester TPA as well as in two cell lines devoid of cytoplasmic intermediate filament proteins, the human adrenal cortex carcinoma-derived cells SW-13 and the clone C6-M-D4 derived from the rat glial cell line C6. Our results show that the inhibition of proliferation and the induction of vimentin synthesis observed in TPA-treated MPC-11 populations are not paralleled by changes in the lamin complement of these cells, which contain lamin B but lack lamins A and C. Furthermore, the analysis performed on SW-13 and C6-M-D4 cell lines clearly demonstrates that mammalian somatic cells display considerable variations in lamin expression and indicates that lamin B may be the only lamin species constitutively expressed in mammalian cells.

Regulation of 21-hydroxylase gene expression

The steroid 21-hydroxylase (21-OH) gene is selectively expressed in the adrenal cortex and is transcriptionally regulated by ACTH. We examined the role of the 5'-flanking sequences of 21-OH in this regulated expression by analyzing their ability to direct the expression of a human growth hormone (hGH) reporter gene upon transfection into Y1 mouse adrenocortical tumor cells. The 330 bp of 5'-flanking sequences directed basal and hormonally-inducible expression of hGH in Y1 cells, but did not direct expression in I-10 mouse testicular Leydig cells. Both constitutive and hormonally-inducible expression required a functional cAMP-dependent protein kinase. These results indicate that the first 330 bp of 5'-flanking sequences of the 21-OH gene contain sufficient information for cell-specific and hormonally regulated expression, and that this expression requires the integrity of cAMP-dependent protein kinase. Markedly lower expression of hGH was seen when 156 bp of 5'-flanking sequences were placed in front of the reporter gene, suggesting that sequences between -330 and -156 are essential for expression. The addition of sequences from -330 to -150 to the p-156GH plasmid, in either the correct or the reverse orientation, restored promoter activity to approximately the level obtained with the 330 bp of 5'-flanking sequences. Moreover, the addition of sequences from -230 to -150 increased by 5-fold the expression of hGH driven by the heterologous thymidine kinase promoter. Based on these results, we conclude that an enhancer element is contained within the sequences from 230 to 150 bp upstream of the transcription initiation site.

Recovery of responsiveness to ACTH and cAMP in a protein kinase-defective adrenal cell mutant following transfection with a protein kinase gene

The cause and effect relationship between mutations in cAMP-dependent protein kinase activity and resistance of adrenocortical tumor cells to ACTH and cAMP was evaluated by transfection with cloned cDNAs encoding subunits of the mouse cAMP-dependent protein kinase. Protein kinase defective, Kin 8 adrenocortical tumor cells were transfected with pRev [an expression vector encoding the regulatory subunit of the type 1 cAMP-dependent protein kinase (RI)] or with pC alpha ev [an expression vector encoding the catalytic subunit of cAMP-dependent protein kinase (C)]. The pC alpha ev transformant recovered cAMP responsive protein kinase activity, whereas the pRev transformant recovered cAMP-binding activity, but did not recover cAMP responsive protein kinase activity. The pC alpha ev transformant concomitantly recovered steroidogenic and morphologic responsiveness to ACTH- and 8-bromo-cAMP, whereas the pRev transformant remained resistant to these effects of the hormone and cyclic nucleotide. Since Kin 8 cells recovered their responsiveness to ACTH and 8-bromo-cAMP following transfection with pC alpha ev we suggest that the defect in cAMP-dependent protein kinase activity is directly responsible for the ACTH- and cAMP-resistant phenotype of the Kin 8 mutant.

Visualization of adrenocortical carcinoma lung metastases with iodine-131 labeled 6B-iodomethylnorcholesterol (NP-59)

This case report describes visualization of lung metastases secondary to adrenocortical carcinoma using I-131 labeled 6B-iodomethyl-19-norcholesterol (NP-59) in a 26-year-old woman with a recurrence of Cushing's syndrome one year following surgical removal of the primary tumor.

The effects of taxol, a microtubule-stabilizing drug, on steroidogenic cells

The effects of taxol on steroid production and microtubule polymerization were examined using Y-1 adrenocortical tumor cells, MLTC-1 Leydig tumor cells, and primary cultures of bovine adrenocortical cells. Taxol inhibited the following steroidogenic processes within the Y-1 and MLTC-1 cells: (1) hormonal increase of steroid production, (2) dibutyryl cyclic AMP-increased steroid production, and (3) hormone-stimulated pregnenolone production. The inhibitory action of taxol was concentration dependent and also resulted in an increase in cytoplasmic microtubules. In addition, the inhibitory action of taxol on hormone-stimulated steroid production was reversible. Taxol appeared to inhibit cholesterol movement to the mitochondrial site of cholesterol side-chain cleavage enzyme but did not affect overall protein synthesis. Interestingly, taxol did not affect hormone-stimulated steroid production in bovine adrenocortical cells. This lack of inhibition may correspond to the ultrastructural observation that microtubule bundling after taxol treatment was observed in the tumor cells but not in similarly treated bovine adrenal cells. With this conflicting information between cell types, a direct relationship between taxol treatment and inhibition of steroid production has not been established. However, these results suggest that taxol alters the rate of transport of cholesterol to the cholesterol side-chain cleavage enzyme within the steroidogenic tumor cells.

Prolonged survival following six pulmonary resections for metastatic adrenal cortical carcinoma: a case report

A case is presented of prolonged survival following multiple thoracotomies performed for metastatic adrenal cortical carcinoma that was refractory to other treatment modalities. In selected patients with isolated metastases to the lungs, repeated surgical resection may offer the only possibility for cure or extended palliation.

Mutations in cyclic AMP-dependent protein kinase and corticotropin (ACTH)-sensitive adenylate cyclase affect adrenal steroidogenesis

Two groups of mutant clones were isolated from YI adrenocortical tumor cells. One group, Y1(Kin), exhibited altered cytosolic cyclic AMP-dependent protein kinase activity; the second group, Y1(Cyc), exhibited diminished corticotropin-responsive adenylate cyclase activity. Steroidogenic responses to corticotropin and cyclic nucleotides closely paralleled cyclic AMP-dependent protein kinase activity in the Y1(Kin) mutants. In Y1(Cyc) mutants, corticotropin had little effect on steroidogenesis, whereas cyclic nucleotides were fully active. These data imply that adenylate cyclase and cyclic AMP-dependent protein kinase are obligatory components of the corticotropin-stimulated steroidogenic pathway.

Hormonal regulation of initiation of DNA synthesis and of differentiated function in Y-1 adrenal cortical cells

ACTH, 8-Br-cAMP, and serum deprivation arrested Y-1 functional mouse adrenal tumor cells in the G1 phase of the cell cycle. Though ACTH and 8-Br-cAMP treated cells were larger with increased macromolecular synthetic rates compared to cells arrested in G1 by serum removal, a similar 8- to 10-hours lag to initiation of DNA synthesis was observed after either ACTH or 8-Br-cAMP removal or after serum addition. After the 8- to 10-hour lag period, cells entered S phase exponentially. ACTH or 8-Br-cAMP opposed serum induced DNA synthesis initiation only when added prior to S. Once commitment to DNA synthesis occurred, ACTH or 8-Br-cAMP addition did not inhibit DNA synthesis although 8-Br-cAMP induced a secondary block in G2. Though ACTH and 8-Br-cAMP inhibited serum induced initiation of DNA synthesis and did not affect serum induced cellular hypertrophy, both substances increased the steroidogenic capacity of the cell. ACTH and 8-Br-cAMP thus appear to specifically oppose the stimulatory effects of serum on initiation of DNA synthesis while inducing the differentiated function of the cell.

Biosynthesis of adrenodoxin in mouse adrenal tumor cells

ACTH and cAMP stimulate steroidogenesis and the mitochondrial electron transport system for steroid hydroxylation in cultured mouse adrenal cortex tumor cells. During this stimulation, the biosynthesis of adrenodoxin, a non-heme iron protein which is one of the electron transport enzymes, was examined. 14C-labeled adrenodoxin was isolated by employing a purified rabbit antibody to bovine adrenodoxin. The antibody-adrenodoxin precipitates were further purified by acrylamide gel electrophoresis. It was observed that the biosynthesis of adrenodoxin was stimulated in response to ACTH induction and that this stimulation was completely inhibited with cycloheximide and partially inhibited with chloramphenicol. As a result, it was concluded that adrenodoxin requires both mitochondrial and cytosol ribosomal activities for its synthesis and integration into adrenal mitochondria.

Diagnostic features of tumors of the lower thoracic sympathetic chain

Four cases of sympathetic neural tumors of the most inferior portion of the thoracic sympathetic chain are presented. The location of each tumor was such that a primary adrenal tumor might have been considered. However, each tumor was associated with erosion of the ipsilateral lower ribs or vertebral pedicles. Such radiologic findings indicate a primary posterior mediastinal tumor and primary exploration should be transthoracic.