Enzymes, such as protein kinase C (PKC), are ubiquitously expressed by eukaryotes and are an attractive target to guide discovery of new bioactive substances. The PKC signaling path constitutes a ...pivotal mechanism in the regulation of fundamental processes such as protein synthesis, gene expression, and cell proliferation. Consequently, the development of selective, nontoxic PKC inhibitors may provide treatments for cancer or viruses. Only a few natural product PKC inhibitors have been discovered, and some of the most important are alkaloids such as the staurosporines, chelerythrine, and balanol. We report below xestocyclamine A (1) as a new type of polycyclic alkaloid PKC inhibitor. The work leading to the discovery of xestocyclamine A (1) began when the semipure extracts of Xestospongia sp., a soft, brown, massive sponge collected from the Milne Bay province of Papua, New Guinea, exhibited 100% inhibition at 5 mu g/mL against PKC beta .
Six new acetylenic compounds,
1,
7–11, were isolated from the marin sponge
Pellina triangulata. Structures were established using NMR spectroscopy and chemical degradation. Collisional activation ...decomposition (CAD) tandem mass spectrometry of the lithium adducts of the acetylenic compounds was applied to ascertain if charge-remote fragmentation would yield definitive information regarding the site of internal unsaturation in these polyfunctional compounds. Pellynic acid (
1) inhibited inosine monophosphate dehydrogenase (LMPDH)
in vitro.
Six new acetylenic compounds,
1,
7–11, were isolated from the marine sponge
Pellina triangulata. Structures were established using NMR spectroscopy, chemical degradation, and collisional activation decomposition (CAD) tandem mass spectrometry. Pellynic acid (1) inhibited IMPDH.
In cultured MRC-5 cells, ganciclovir (GCV) alone had good activity against both the established AD169 strain (IC50 8 and 9 microM) and a clinical isolate (IC50 14 microM) of human cytomegalovirus ...(CMV), while 3'-azido-3'-deoxythymidine (AZT) was relatively inactive IC50 508 and > 800 (AD169 strain); > 800 microM (clinical isolate). When reductions in plaques were compared against reductions in the cellular metabolism of MTT at all GCV and AZT combination concentrations using an improved 3-dimensional linear regression analysis, AZT had an additive effect on the antiviral activity of GCV against the AD169 strain and potentiated the antiviral activity of GCV against the clinical isolate. Calculations showed that, in the presence of 50 microM AZT, the anti-CMV activity of GCV was unchanged for the AD169 strain, whereas the activity of GCV was increased approximately 5-10-fold for the clinical isolate. An increase in GCV efficacy for the AD169 strain first became apparent at 100 microM AZT with an approximately 3-fold increase in activity. In Swiss-Webster mice, the anti-CMV activity of GCV against murine CMV was unaffected when administered in combination with AZT. GCV given alone subcutaneously had an ED50 of 6 mg/kg which was unaffected by daily intraperitoneal doses of 320 mg/kg AZT. These results suggest that AZT will not adversely affect the efficacy of GCV against CMV in HIV-positive, non-neutropenic patients.
Hereditary hemochromatosis (HH) is the most common autosomal recessive disorder known in humans. A candidate gene for HH called HFE has recently been cloned that encodes a novel member of the major ...histocompatibility complex class I family. Most HH patients are homozygous for a Cys-282→Tyr (C282Y) mutation in HFE gene, which has been shown to disrupt interaction with β
2
-microglobulin; a second mutation, His-63→Asp (H63D), is enriched in HH patients who are heterozygous for C282Y mutation. The aims of this study were to determine the effects of the C282Y and H63D mutations on the cellular trafficking and degradation of the HFE protein in transfected COS-7 cells. The results indicate that, while the wild-type and H63D HFE proteins associate with β
2
-microglobulin and are expressed on the cell surface of COS-7 cells, these capabilities are lost by the C282Y HFE protein. We present biochemical and immunofluorescence data that indicate that the C282Y mutant protein: (
i
) is retained in the endoplasmic reticulum and middle Golgi compartment, (
ii
) fails to undergo late Golgi processing, and (
iii
) is subject to accelerated degradation. The block in intracellular transport, accelerated turnover, and failure of the C282Y protein to be presented normally on the cell surface provide a possible basis for impaired function of this mutant protein in HH.
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