Signalling Inhibitors Against Mycobacterium tuberculosis – Early Days of a New Therapeutic Concept in Tuberculosis

Abstract

Tuberculosis causes nearly two million deaths per year world-wide. In addition multidrug-resistant mycobacterial strains rapidly emerge so novel therapeutic approaches are needed. Recently, several promising mycobacterial target molecules were identified, which are involved in bacterial or host cell signalling e.g. the serine/threonine protein kinases, PknB and PknG, NAD kinase and the NAD synthetase. Here we describe some early efforts in the development of novel signal transduction inhibitory anti-mycobacterial drugs using a multiple target approach, with special emphasis on the kinase inhibitory field. Initially, we are using the Nested Chemical Library (NCL) technology and pharmacophore modelling. A hit-finding library, consisting of approximately 19000 small molecules with a bias for prototypic kinase inhibitors from our NCL library and commercial sources was virtually screened against these validated target molecules. Protein structures for the virtual screening were taken from the published three dimensional crystal structures of the enzymes. The hits from the virtual screening were subsequently tested in enzymatic assay systems. Potent hits were then tested for biological activity in macrophages, infected with mycobacteria. The final goal of this exercise is not only to identify potent anti-mycobacterial substances, but also a common pharmacophore for the mycobacterial target PknG in combination with PknB, NAD kinase and/or NAD synthetase. This common pharmacophore still needs to be a unique pharmacophore for the mycobacterial target proteins over human off-targets. Such a pharmacophore might then drive the optimization of a completely new profile of an antibiotic agent with activity against latent mycobacteria and resistance mycobacterial strains.

NMN/NaMN Adenylyltransferase (NMNAT) and NAD Kinase (NADK) Inhibitors: Chemistry and Potential Therapeutic Applications

“…In 2008, Hegymegi-Barakonyi et al [74] presented a new concept and some preliminary data on a multiple target approach to inhibit cell signalling pathways of M. tuberculosis. Specially, they focussed on four main targets (PknB, PknG, NAD kinase and NAD synthetase) and the idea was to identify a common pharmacophore for at least two of these targets.…”

Antimycobacterial activity of UDP-galactopyranose mutase inhibitors

“…Phorbol myristate acetate-differentiated THP-1 macrophages were infected with M. bovis BCG [15]. Inhibitors at a final concentration of 5 g/mL (for 24 h) and 10 g/mL (for the following 24 h) were added and incubated for 24 h and 48 h, respectively.…”

“…Inhibitors at a final concentration of 5 g/mL (for 24 h) and 10 g/mL (for the following 24 h) were added and incubated for 24 h and 48 h, respectively. Cells were lysed and counting was performed [15].…”

Protein cysteine phosphorylation of SarA/MgrA family transcriptional regulators mediates bacterial virulence and antibiotic resistance

“…However, it wasn't until recently that eukaryotic-like Ser/Thr/Tyr phosphorylation in bacteria started to receive significant attention (6)(7)(8). Particularly, in pathogenic bacteria such as Mycobacterium tuberculosis and Staphylococcus aureus, eukaryotic-like Ser/Thr kinases (and associated phosphatases) have often been shown to participate in virulence functions (5,(9)(10)(11). The kinase/phosphatase pairs are known as Stks/Stps in bacteria; the kinase Stk1 has been called as PknB or Stk, and the phosphatase Stp1 as Stp (9).…”