Erwin Paul Schreiner

Selective inhibition of cotranslational translocation of vascular cell adhesion molecule 1

Increased expression of vascular cell adhesion molecule 1 (VCAM1) is associated with a variety of chronic inflammatory conditions, making its expression and function a target for therapeutic intervention. We have recently identified CAM741, a derivative of a fungus-derived cyclopeptolide that acts as a selective inhibitor of VCAM1 synthesis in endothelial cells. Here we show that the compound represses the biosynthesis of VCAM1 in cells by blocking the process of cotranslational translocation, which is dependent on the signal peptide of VCAM1. CAM741 does not inhibit targeting of the VCAM1 nascent chains to the translocon channel but prevents translocation to the luminal side of the endoplasmic reticulum (ER), through a process that involves the translocon component Sec61β. Consequently, the VCAM1 precursor protein is synthesized towards the cytosolic compartment of the cells, where it is degraded. Our results indicate that the inhibition of cotranslational translocation with low-molecular-mass compounds, using specificity conferred by signal peptides, can modulate the biosynthesis of certain secreted and/or membrane proteins. In addition, they highlight cotranslational translocation at the ER membrane as a potential target for drug discovery.

Inhibition of Vascular Endothelial Growth Factor Cotranslational Translocation by the Cyclopeptolide CAM741

The cyclopeptolide CAM741 inhibits cotranslational translocation of vascular cell adhesion molecule 1 (VCAM1), which is dependent on its signal peptide. We now describe the identification of the signal peptide of vascular endothelial growth factor (VEGF) as the second target of CAM741. The mechanism by which the compound inhibits translocation of VEGF is very similar or identical to that of VCAM1, although the signal peptides share no obvious sequence similarities. By mutagenesis of the VEGF signal peptide, two important regions, located in the N-terminal and hydrophobic segments, were identified as critical for compound sensitivity. CAM741 alters positioning of the VEGF signal peptide at the translocon, and increasing hydrophobicity in the h-region reduces compound sensitivity and causes a different, possibly more efficient, interaction with the translocon. Although CAM741 is effective against translocation of both VEGF and VCAM1, the derivative NFI028 is able to inhibit only VCAM1, suggesting that chemical derivatization can alter not only potency, but also the specificity of the compounds.

6-[2-(adamantylidene)-hydroxybenzoxazole]-O-sulfamate, a steroid sulfatase inhibitor for the treatment of androgen- and estrogen-dependent diseases.

Steroid sulfatase (STS) offers a new target for the treatment of steroid hormone-dependent diseases, such as breast and prostate cancer and androgen-dependent skin diseases. We here characterize a novel non-estrogenic inhibitor of the enzyme, namely 6-[2-(adamantylidene)-hydroxybenzoxazole]-O-sulfamate (AHBS), with special attention to its potential use in the treatment of acne. The compound blocks STS activity in homogenates of human skin with IC(50)=16 nM. Following a single oral dose (5 mg/kg) in rats, the compound blocks STS in the skin by 95% at 8 h, followed by recovery of activity over 5 days. Following topical application to the skin, both in vitro and in vivo, AHBS passes through the stratum corneum leading to inhibition of STS activity in the dermal compartment with rapid onset and long duration. Topical application of AHBS to Göttingen minipigs for a period of 2 weeks does not induce symptoms of ichthyosis as seen in STS-deficient human subjects, but leads to a reduction of sebum secretion to the skin surface. Based on these data, clinical studies with AHBS in acne patients are warranted, in order to verify the hypothesis on the importance of the sulfatase pathway in androgen-dependent skin diseases.

Inhibitors of vascular cell adhesion molecule-1 expression

Leukocyte extravasation, a complex multistep process involving the selective recruitment of white blood cell subpopulations to specific tissues, is finely regulated to a large extent by inducible adhesion molecules on the endothelium. Secreted mediators such as tumour necrosis factor alpha (TNF-α) transcriptionally activate endothelial cells at sites of injury or inflammation, resulting in the localised de novo synthesis of cell surface proteins such as vascular cell adhesion molecule-1 (VCAM-1). Circulating leukocytes bearing the VCAM1 ligand, namely the integrin very late antigen4 (VLA-4), then bind to their corresponding adhesion receptor that is newly expressed on the luminal surface of postcapillary venules. Preclinical data strongly suggest that the VCAM-1/VLA-4 adhesion pathway significantly contributes to the pathogenesis of numerous diseases including asthma, atherosclerosis, inflammatory bowel disease, multiple sclerosis and rheumatoid arthritis. VCAM-1 thus represents an attractive target for drug intervention due to its central role in sequential events leading to the transendothelial migration of leukocytes (e.g., T and B lymphocytes, eosinophils, monocytes). This article focuses on patents claiming inhibition of VCAM-1 gene and protein expression, primarily covering antioxidants, antisense oligonucleotides, cyclic depsipeptides of the HUN-7293 type and small heterocyclic compounds.