Biomedical subjects

D L Confer

Publications and source records attributed to D L Confer.

24 records · Page 2Linked to original sources

PubMed1987

Rapid transcriptional down-regulation of c-myc expression during cyclic adenosine monophosphate-promoted differentiation of leukemic cells.

Pharmacologic elevation of cyclic AMP (cAMP) promotes growth arrest and differentiation in a variety of transformed mammalian cells, including the HL-60 human promyelocytic leukemia cell line. However, mechanisms underlying this phenomenon are poorly understood. Because cellular oncogenes play a pivotal role in regulating proliferation and differentiation, we examined whether cAMP-promoted differentiation of HL-60 was preceded by a decrease in the expression of c-myc, a cellular oncogene both amplified and constitutively expressed in HL-60. We find that cyclic AMP elevation in HL-60 caused by three different pharmacologic regimens is followed by an abrupt, greater than 90% decrease in steady state c-myc mRNA levels within 3 h, well before detectable changes in proliferation and differentiation. This decrease, which occurs despite protein synthetic blockade, is attributable to transcriptional down-regulation of c-myc and is accompanied by changes in chromatin structure near c-myc promoter sites. Our findings establish that cAMP, a ubiquitous intracellular regulatory messenger previously known only to enhance gene transcriptional activity in higher eukaryotic cells, can also suppress transcription of a cellular oncogene, thereby suggesting a potential mechanism for cAMP-promoted differentiation.

1-Methyl-3-isobutylxanthine↗

PubMed1985

Bordetella adenylate cyclase: host toxicity and diagnostic utility.

Two toxins from Bordetella pertussis, pertussis toxin and Bordetella adenylate cyclase, cause profound disruptions of cAMP metabolism in mammalian cells. While the role of each toxin in the whooping cough syndrome is unknown, it is highly likely that together they confer on the organism an important proliferative advantage. Intact B. pertussis cells express large amounts of adenylate cyclase activity on their exterior surface. In a presently unknown fashion, this enzyme can enter human phagocytes, elevate cellular cAMP and impair host defense. We reasoned that this unusual enzyme might serve to signal the presence of B. pertussis in nasopharyngeal swabs from infected persons. Here we report a series of in vitro experiments which confirm the feasibility of such an approach. We find that calcium alginate swabs containing as few as 100 B. pertussis organisms produce readily detectable amounts of cAMP in our assay. Nasopharyngeal secretions swabbed from healthy volunteers, however produced no detectable cAMP alone and did not affect the production of cAMP by B. pertussis. We have also tested pure cultures of four common bacterial pathogens (Haemophilus influenzae, Streptococcus pyogenes, Staphylococcus aureus, and Escherichia coli) which may be co-isolated in clinical whooping cough and find that none interferes with the detection of B. pertussis. We conclude that the unique adenylate cyclase of B. pertussis might be a valuable diagnostic device.

Adenylyl Cyclases↗

PubMed1984

Bordetella adenylate cyclase toxin: entry of bacterial adenylate cyclase into mammalian cells.

We have identified an adenylate cyclase toxin in urea extracts and culture supernatant fluids of Bordetella pertussis (2). The ability of this toxin and the lack of a strong correlation between its activity and adenylate cyclase activity found in urea extracts suggest that it is an oligomer of readily dissociable subunits. The mechanism by which Bordetella adenylate cyclase toxin interacts with target cells is unknown, but polyvalent cations are necessary. Neutrophils exposed to the toxin acquire a 39,000 Mr protein that can also be photoaffinity labeled with 32P-ATP. We anticipate that this protein will prove to be a catalytic component of Bordetella adenylate cyclase toxin. Susceptible cells exposed to Bordetella adenylate cyclase toxin are functionally aberrant. In phagocytes, decreased bactericidal capacity may be important in the pathogenesis of human whooping cough and other Bordetella infections occurring in domestic animals. The effects of the toxin on neoplastic cells may offer new insights into the factors controlling their growth and differentiation. Bordetella adenylate cyclase toxin is a unique bacterial product. Further purification and characterization of this toxin will add to our understanding of cell-protein interactions and pathogen-host relationships.

Adenylate Cyclase Toxin↗

PubMed1983

Antineoplastic effects of Bordetella pertussis adenylate cyclase.

Urea extracts of B. pertussis, but not B. bronchiseptica, cause large and sustained intracellular cAMP elevation in several neoplastic cell lines. These cAMP elevations are associated with growth inhibition (HL-60, Friend erythroleukemia) and a phenotypic change/differentiation (HL-60, L1210). B. pertussis extract injections prolong survival of L1210 tumor-bearing mice. Pretreatment of L1210 cells with B. pertussis extract both delays mortality and induces growth of solid tumors instead of ascites in subsequently inoculated mice. We conclude that B. pertussis adenylate cyclase is capable of invading a variety of neoplastic cells to catalyze the intracellular formation of large amounts of cAMP. These cAMP elevations are durable and promote growth arrest, differentiation, or phenotypic alterations reflected in altered biologic behavior. B. pertussis adenylate cyclase should prove to be a useful tool for manipulating cAMP levels in neoplastic cells to elucidate the role of cAMP in malignant transformation.

Adenylyl Cyclases↗

PubMed1982

Phagocyte impotence caused by an invasive bacterial adenylate cyclase.

For unknown reasons, humans infected with the bacterium Bordetella pertussis are exceptionally vulnerable to secondary infections. Bordetella species elaborate a soluble, heat-stable, and highly active adenylate cyclase. This enzyme is internalized by phagocytic cells and catalyzes the unregulated formation of adenosine 3',5'-monophosphate (cyclic AMP), thereby disrupting normal cellular function. This unusual phenomenon may explain Bordetella-induced aphylaxis and may prove to be useful for investigating a variety of cyclic AMP-governed processes.

Adenylyl Cyclases↗

PubMed1982

Pathogen-host jujitsu: phagocyte impotence caused by internalized bacterial adenylate cyclase.

Humans and animals infected with Bordetella species show evidence of impaired host defenses. These pathogenic bacteria produce a unique adenylate cyclase which enters human phagocytes and catalyzes the unregulated formation of cAMP, a known cellular inhibitor. This unique pathogen-host interaction may explain the unusual features of human B. pertussis infection and represents a powerful new probe for the investigation of cAMP-governed processes.

Adenylyl Cyclases↗