Biological Profile of the Less Lipophilic and Synthetically More Accessible Bryostatin 7 Closely Resembles That of Bryostatin 1

Abstract

The bryostatins are a group of twenty macrolides isolated by Pettit and coworkers from the marine organism Bugula neritina. Bryostatin 1, the flagship member of the family, has been the subject of intense chemical and biological investigations due to its remarkably diverse biological activities, including promising indications as therapy for cancer, Alzheimer’s disease, and HIV. Other bryostatins, however, have attracted far less attention, most probably due to their relatively low natural abundance and associated scarcity of supply. Among all macrolides in this family, bryostatin 7 is biologically the most potent PKC (protein kinase C) ligand (in terms of binding affinity) and also the first bryostatin to be synthesized in the laboratory. Nonetheless, almost no biological studies have been carried out on this agent. We describe herein the total synthesis of bryostatin 7 based on our pyran annulation technology, which allows for the first detailed biological characterizations of bryostatin 7 with side-by-side comparisons to bryostatin 1. The results suggest that the more easily synthesized and less lipophilic bryostatin 7 may be an effective surrogate for bryostatin 1.

Synthesis, biological, and biophysical studies of DAG-indololactones designed as selective activators of RasGRP

“…The GFP-PKCε, GFP-PKCδ and GFP-RasGRP3 were expressed in LNCaP cells, which we have extensively used for visualization of PKC translocation, as well as for biological analysis of PKC ligands. 38– 40 GFP-PKCα was expressed in CHO cells, since PKCα shows only limited translocation in response to phorbol esters in LNCaP cells, presumably reflecting a low basal level of internal calcium, which functions as a co-activator of classic PKC isoforms. 38 Representative images are presented for PKCα, for PKCε, for PKCδ, and for RasGRP3 (Figure 3A, 3C, 3E, and 2F, respectively).…”

“…38– 40 GFP-PKCα was expressed in CHO cells, since PKCα shows only limited translocation in response to phorbol esters in LNCaP cells, presumably reflecting a low basal level of internal calcium, which functions as a co-activator of classic PKC isoforms. 38 Representative images are presented for PKCα, for PKCε, for PKCδ, and for RasGRP3 (Figure 3A, 3C, 3E, and 2F, respectively). For PKCα and PKCε, which showed substantial differences among ligands, the results were also quantitated as the ratio of membrane/cytoplasmic signal (Figure 3B, 3D, respectively).…”

“…38 Human RasGRP3 was PCR amplified and cloned into the pQBI25fN1 vector using NheI restriction enzyme. Sequence analysis of the construct was conducted by the DNA Minicore (Center for Cancer Research, NCI, National Institutes of Health).…”

Replacement of the bryostatin A- and B-pyran rings with phenyl rings leads to loss of high affinity binding with PKC

“…For the C-ring portion of the molecule an acetate ester at C20, as opposed to the natural bryostatin 1 (2E,4E)-octa-2,4-dienoate ester, was chosen. The C20 ester is synthetically more convenient, and through the synthesis of bryostatin 7 (K i = 0.26 nM) 22 and a C20 acetate version of Merle 23 (K i = 0.6 nM) 23 we have shown that this substitution has a minimal effect on PKC binding.…”

The expression of SLAMF7 levels in malignant B cells: a novel therapeutic pathway for patients with CLL

“…Differences in the extent and effect of the two PKC activators (PMA and Bryostatin) have been reported (Wender et al, 1988;Kedei et al, 2013a;Kedei et al, 2013b). In contrast to PMA, Bryostatins do not have tumour promoting activity, but rather show anti-neoplastic features (Hennings et al, 1987;Nakagawa et al, 2009).…”