Glycogen synthase kinase 3 (GSK3), a constitutively acting multi-functional serine threonine kinase is involved in diverse physiological pathways ranging from metabolism, cell cycle, gene expression, development and oncogenesis to neuroprotection. These diverse multiple functions attributed to GSK3 can be explained by variety of substrates like glycogen synthase, t protein and b catenin that are phosphorylated leading to their inactivation. GSK3 has been implicated in various diseases such as diabetes, inflammation, cancer, Alzheimer's and bipolar disorder. GSK3 negatively regulates insulin-mediated glycogen synthesis and glucose homeostasis, and increased expression and activity of GSK3 has been reported in type II diabetics and obese animal models. Consequently, inhibitors of GSK3 have been demonstrated to have anti-diabetic effects in vitro and in animal models. However, inhibition of GSK3 poses a challenge as achieving selectivity of an over achieving kinase involved in various pathways with multiple substrates may lead to side effects and toxicity. The primary concern is developing inhibitors of GSK3 that are anti-diabetic but do not lead to up-regulation of oncogenes. The focus of this review is the recent advances and the challenges surrounding GSK3 as an anti-diabetic therapeutic target.

ABSTRACTp38 mitogen-activated protein kinase (p38 MAPK) plays an important role in the key cellular processes related to inflammation. Several small molecule inhibitors of p38 MAPK therefore have been evaluated for their anti-inflammatory potential and progressed from early discovery to late phase clinical trials. Most of these efforts however have failed due to severe toxicity concerns. Since p38 MAPK has several downstream substrates, inhibition of p38 MAPK, therefore, leads to the modulation of all its substrates, resulting into a dis-balance of pro- and anti-inflammatory response and multiple toxicity concerns. Targeting p38MAPK MAPKAPK2 (MK2), one of the downstream substrates of p38 MAPK directly, is expected to be a better anti-inflammatory approach without having any toxicity concerns. In this manuscript, we are reporting biological data of representative MK2 inhibitor to validate its anti-inflammatory potential and a comparison of p38 MAPK and MK2 inhibitors in cell based assays to understand their relative toxicities.

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Phosphodiesterases (PDE) are enzymes that catalyze the hydrolysis of cAMP/cGMP to 5′-AMP/GMP. In vitro assays have routinely assayed cAMP/cGMP levels as a direct indicator of PDE activity. Earlier PDE assays depended on radiometric detection of radiolabeled cAMP. Of late, nonradiometric cAMP detection systems have been developed that are cheaper and more amenable to high-throughput screening. Two such assays, namely the enzyme fragment complementation technology and homogeneous time-resolved fluorescence assays, are currently used for monitoring cAMP as a correlate for G-protein-coupled-receptor-induced cellular signaling events. Here, we have compared and validated both of these assays for the measurement of PDE4 enzyme activity in cell-free systems.