Tyrosine kinases as essential cellular cofactors and potential therapeutic targets for human immunodeficiency virus infection.

The Human Immunodeficiency Virus (HIV) is the cause of the AIDS disease. To date, more than 30 million people worldwide are infected with HIV—1, which causes two millions deaths each year. The pandemic is still ongoing, with three million new infections every year. Even though the current arsenal of anti—HIV drugs is composed of more than twenty different molecules, it became clear that the chemotherapeutic approach will not be able to cure AIDS, at least in its current form. It is essential, in order to develop more effective ways of treating this disease, to better understand the interplay of HIV with its cellular host, in fact HIV—1 is an obligatory intracellular parasite that takes advantage of the host cell metabolism for its own replication. HIV—1 takes control of virtually every aspect of cell metabolism by changing the functional properties of key signaling cellular proteins, thus triggering virus—specific signal transduction pathways. In this review, we will summarize the current knowledge about the role(s) of cellular tyrosine kinases in HIV infection and their potential therapeutic exploitation.

Molecular docking, design, synthesis and biological evaluation of novel 2,3-aryl-thiazolidin-4-ones as potent NNRTIs.

Nonnucleoside reverse transcriptase inhibitors (NNRTIs) remain the most promising anti-AIDS agents that target the HIV-1 reverse transcriptase enzyme (RT). However, the efficiency of approved NNRTI drugs has decreased by the appearance of drug-resistant viruses and side effects upon long-term usage. Thus, there is an urgent need for developing new, potent NNRTIs with broad spectrum against HIV-1 virus and with improved properties. In this study, a series of thiazolidinone derivatives was designed based on a butterfly mimicking scaffold consisting of a substituted benzothiazolyl moiety connected with a substituted phenyl ring via a thiazolidinone moiety. The most promising derivatives were selected using molecular docking analysis and PASS prediction program, synthesized and evaluated for HIV-1 RT inhibition. Five out of fifteen tested compounds exhibited good inhibitory action. It was observed that the presence of Cl or CN substituents at the position 6 of the benzothiazole ring in combination with two fluoro atoms at the ortho-positions or a hydrogen acceptor substituent at the 4-position of the phenyl ring are favourable for the HIV RT inhibitory activity.

Overcoming the drug resistance problem with second-generation tyrosine kinase inhibitors: from enzymology to structural models.

Protein phosphorylation is one of the major pathways used by eukaryotic cells to propagate signals to the final effectors, regulating multiple aspects of the living cell, such as metabolism, growth, differentiation, adhesion, motility, genome stability and death. In this context, tyrosine kinases (TKs) play a central role in signal transduction and their overexpression or disregulated activity has been implicated in tumor onset and malignancy progression. To date, eight TKs inhibitors have been approved by FDA for the treatment of specific tumors. In spite of their efficacy, insurgence of resistance is a common feature after prolonged administration. The selective pressure by these drugs, in fact, induces clonal expansion of subsets of cancer cells harboring TKs mutations, leading to decreased inhibition potency. Alternatively, resistance to TK inhibitors can be acquired through the activation of others, often unrelated, TKs. For this reason, while stringent target selectivity of TKs inhibitors has been always considered a desirable feature in order to limit toxicity, molecules targeting different TKs have been recently shown to be promising anti-cancer agents as well. Understanding the molecular mechanisms that confer resistance to TK inhibitors, through a combination of enzymatic, structural and cellular studies, is essential in the development of second generation inhibitors active also towards drug resistant tumors.

DNA polymerases and oxidative damage: friends or foes?

DNA is modified by many mutagens, including reactive oxygen species (ROS). When ROS react with DNA, various kinds of modified base and/or sugar moieties are produced. One of the most important oxidative DNA lesions is 7,8-dihydro-8-oxoguanine (8-oxo-G). Contrary to normal deoxyguanosine, 8-oxo-G favors a syn conformation, enabling it to form a Hoogsteen base pair with adenine which resembles a normal Watson-Crick base pair in shape and geometry. As a consequence, most human DNA polymerases (pols) studied so far show significant error-prone bypass of 8-oxo-G. The 1,2-dihydro-2-oxoadenine (2-OH-A) is another common DNA lesion produced by ROS. 2-OH-A possesses significant mutagenic potential in living cells. When challenged with a 2-OH-A lesion on the template, DNA pols often misinsert G and C nucleotides, with various efficiencies depending upon the sequence context. We have recently shown that human DNA pol lambda is extremely efficient in performing error-free bypass of both 8-oxo-G and 2-OH-A lesions, and that its efficiency is positively modulated by the auxiliary factors proliferating cell nuclear antigen and replication protein A. In this review we will summarize the most recent advancements in the field of oxidative DNA damage tolerance with special emphasis on the pro- and anti-mutagenic roles of DNA pols and auxiliary proteins.