Background: Nucleocytoplasmic transport of Hxk2 is mediated by the ␣/␤-importins (Kap60/Kap95) and the Xpo1(Crm1) exportin. Results: Hxk2 phosphorylation affects its subcellular localization and its interaction with karyopherins Kap60 and Xpo1. Conclusion:The shuttling back and forth of Hxk2 between the nucleus and the cytoplasm is regulated by phosphorylation and dephosphorylation of serine 14. Significance: Regulating the subcellular distribution of Hxk2 represents a novel physiological function mediated by Snf1 and Glc7-Reg1 proteins.

By synthesis and biological studies of new naphthalene analogues of combretastatins, we have found that the naphthalene is a good surrogate for the isovanillin moiety (3-hydroxy-4-methoxyphenyl) of combretastatin A-4, always generating highly cytotoxic analogues when combined with the 3,4,5-trimethoxyphenyl or related systems. On the other hand, when the naphthalene replaces the 3,4,5-trimethoxyphenyl moiety, the cytotoxic activity is largely decreased. The most cytotoxic naphthalene analogues of combretastatins, which also produce inhibition of tubulin polymerization, exerted their antimitotic effects through microtubule network disruption and subsequent G(2)/M arrest of the cell cycle in human cancer cells.

Hexokinase 2 (Hxk2) from Saccharomyces cerevisiae was one of the first metabolic enzymes described as a multifunctional protein. Hxk2 has a double subcellular localization; it functions as a glycolytic enzyme in the cytoplasm and as a regulator of gene transcription of several Mig1-regulated genes in the nucleus. However, the mechanism by which Hxk2 enters and leaves the nucleus is still unknown. In low glucose conditions, Hxk2 is phosphorylated at serine 14, but how this phosphorylation may affect glucose signaling is also unknown at the moment. Here we report that the Hxk2 protein is an export substrate of the carrier protein Xpo1 (Crm1). We also show that the Hxk2 nuclear export and the binding of Hxk2 and Xpo1 involve two leucine-rich nuclear export signals (NES) located between leucine 23 and isoleucine 33 (NES1) and between leucine 310 and leucine 318 (NES2). We also show that the Hxk2 phosphorylation at serine 14 promotes Hxk2 export by facilitating the association of Hxk2 with Xpo1. Our study uncovers a new cargo for the Xpo1 yeast exportin and identifies Hxk2 phosphorylation at serine 14 as a regulatory mechanism that controls its nuclear exit in function of the glucose levels.Transport of macromolecules across the nuclear envelope occurs through nuclear pore complexes, which are embedded between the inner and the outer nuclear membrane (1). Whereas the protein components of the nuclear pore complex are largely stationary within the pore, soluble transport factors can be freely exchanged between the nuclear and the cytoplasmic compartment. Saccharomyces cerevisiae has several importin ␤-related proteins that are nuclear transport receptors which bind sequences on their transport cargos. Among the importin-␤ family members, the Xpo1 (Crm1) carrier is the major nuclear export receptor in higher eukaryotes as well as in the yeast S. cerevisiae. Xpo1 is the receptor for proteins containing leucine-rich nuclear export signals

Hkx2 (hexokinase 2) from Saccharomyces cerevisiae was one of the first metabolic enzymes described as a multifunctional protein. Hxk2 has a double subcellular localization: it functions as a glycolytic enzyme in the cytoplasm and as a regulator of gene transcription of several Mig1-regulated genes in the nucleus. To get more insights into the structure–function relationships of the Hxk2 protein, we followed two different approaches. In the first, we deleted the last eight amino acids of Hxk2 and replaced Ser304 with phenylalanine to generate Hxk2wca. Analysis of this mutant demonstrated that these domains play an essential role in the catalytic activity of yeast Hxk2, but has no effect on the regulatory function of this protein. In the second, we analysed whether amino acids from Lys6 to Met15 of Hxk2 (Hxk2wrf) are essential for the regulatory role of Hxk2 and whether there is an effect on the hexose kinase activity of this protein. In the present paper, we report that the Hxk2wca mutant protein interacts with the Mig1 transcriptional repressor and the Snf1 protein kinase in the nucleus at the level of the SUC2–Mig1 repressor complex. We have demonstrated that Hxk2wca maintained full regulatory function because the glucose-repression signalling of the wild-type machinery is maintained. We also report that the Hxk2wrf mutant allele is incapable of glucose repression signalling because it does not interact with Mig1 at the level of the SUC2–Mig1 repressor complex. The two mutants, Hxk2wca and Hxk2wrf retain single functions, as a transcriptional factor or as an enzyme with hexose-phosphorylating activity, but have lost the original bifunctionality of Hxk2.

Background: Yeast hexokinase 2 shuttles in and out of nucleus in response to glucose availability. Results: Hexokinase 2 enters the nucleus by binding Kap60 through a nuclear localization sequence in the presence of Kap95. Conclusion:The karyopherins Kap60 and Kap95 are necessary for efficient nuclear import of hexokinase 2. Significance: The current study has identified a new pathway for Hxk2 import into the nucleus.

Colchicine site ligands with indole B rings are potent tubulin polymerization inhibitors. Structural modifications at the indole 3-position of 1-methyl-5-indolyl-based isocombretastatins (1,1-diarylethenes) and phenstatins endowed them with anchors for further derivatization and resulted in highly potent compounds. The substituted derivatives displayed potent cytotoxicity against several human cancer cell lines due to tubulin inhibition, as shown by cell cycle analysis, confocal microscopy, and tubulin polymerization inhibitory activity studies and promoted cell killing mediated by caspase-3 activation. Binding at the colchicine site was confirmed by means of fluorescence measurements of MTC displacement. Molecular modeling suggests that the tropolone-binding region of the colchicine site of tubulin can adapt to hosting small polar substituents. Isocombretastatins accepted substitutions better than phenstatins, and the highest potencies were achieved for the cyano and hydroxyiminomethyl substituents, with TPI values in the submicromolar range and cytotoxicities in the subnanomolar range. A 3,4,5-trimethoxyphenyl ring usually afforded more potent derivatives than a 2,3,4-trimethoxyphenyl ring.

Tubulin, the microtubules and their dynamic behavior are amongst the most successful antitumor, antifungal, antiparasitic, and herbicidal drug targets. Sulfonamides are exemplary drugs with applications in the clinic, in veterinary and in the agrochemical industry. This review summarizes the actual state and recent progress of both fields looking from the double point of view of the target and its drugs, with special focus onto the structural aspects. The article starts with a brief description of tubulin structure and its dynamic assembly and disassembly into microtubules and other polymers. Posttranslational modifications and the many cellular means of regulating and modulating tubulin's biology are briefly presented in the tubulin code. Next, the structurally characterized drug binding sites, their occupying drugs and the effects they induce are described, emphasizing on the structural requirements for high potency, selectivity, and low toxicity. The second part starts with a summary of the favorable and highly tunable combination of physical-chemical and biological properties that render sulfonamides a prototypical example of privileged scaffolds with representatives in many therapeutic areas. A complete description of tubulin-binding sulfonamides is provided, covering the different species and drug sites. Some of the antimitotic sulfonamides have met with very successful Med Res Rev. 2019;39:775-830. wileyonlinelibrary.com/journal/med © 2018 Wiley Periodicals, Inc. | 775applications and others less so, thus illustrating the advances, limitations, and future perspectives of the field.All of them combine in a mechanism of action and a clinical outcome that conform efficient drugs. K E Y W O R D S molecular mechanisms, sulfonamides, tubulin binding drugs, tubulin binding sites 1 | INTRODUCTION Drugs targeting tubulin and the microtubules (tubulin binding drugs [TBDs]) are amongst the most successful antitumor, antifungal, antiparasitic, and herbicidal agents with applications in the clinic, in veterinary and in the agrochemical industry. Recently, the combination of computational methods, medicinal chemistry, biochemistry, structural biology, and cell biology is starting to unravel the intricacies of tubulin binding drugs and of the microtubules themselves, thus paving the way towards new and better TBDs. New methodological advances such as the high resolution cryo-electron microscopy, the imaging of individual microtubule dynamics, and the achievement of recombinant tubulin, altogether with more established methodologies for the study of the microtubules have combined to provide a sharper view of the structure and function of these essential cell components and their interactions with clinically important drugs. The sulfonamides are a prototypical example of privileged scaffolds, with representatives in many therapeutic areas, due to a combination of favorable and highly tunable physical-chemical and biological properties. The early discovery of the dinitroaniline herbicides, and mainly the seminal discovery o...

Colchicine site ligands have proved to be potent inhibitors of tubulin polymerization, which leads them not only to display cytotoxic effects but also vascular disrupting effects on tumour neovasculature. In recent years, many compounds have been designed, synthesized and evaluated in order to improve the potency, stability and physicochemical properties of these agents with the aim of developing an agent that could reach the clinical assay level. Here we analyze the eleven X-ray structures of tubulin in complex with ligands at the colchicine site by dividing it into four different zones of interaction, we review the new compounds that have appeared in the literature since 2008 and that were designed based on any of these X-ray structures and, finally, we describe our latest results in the design of new potent antimitotic indole derivatives that have confirmed the flexibility of one of the zones described for the colchicine site.