AS1949490, an inhibitor of 5′-lipid phosphatase SHIP2, promotes protein kinase C-dependent stabilization of brain-derived neurotrophic factor mRNA in cultured cortical neurons

Drugs targeting SHIP2 demonstrate potent antiproliferative effects irrespective of SHIP2 inhibition

The SH2-containing inositol 5'-phosphatase SHIP2 plays a crucial role in negative regulation of the PI3K/AKT signaling pathway. Putative small molecule inhibitors of SHIP2, AS1949490 and K149 have been reported to elicit a range of beneficial effects in treating or preventing obesity as well as killing cancer cells. However, whether these effects are direct results of SHIP2 inhibition has not been carefully assessed, e.g., in the absence of expression of the protein. Here, we show that these inhibitors alter the PI3K/AKT signaling pathway irrespective of SHIP2 protein expression. Moreover, we found that AS1949490 and K149 alter cell growth in normal and cancer cells lacking both SHIP1 and SHIP2. Overall, our data provide evidence that the antiproliferative effects of AS1949490 and K149 cannot be attributed to SHIP1/2 inhibition.

Discovery of aurones bearing two amine functionalities as SHIP2 inhibitors with insulin-sensitizing effect in rat myotubes

Pharmacological inhibition of the SH2 domain-containing inositol 5-phosphatase 2 (SHIP2) by small-molecule compounds presents an attractive approach to modulate insulin sensitivity. Few drug-like SHIP2 inhibitors have been discovered to date. A series of aurones incorporating key motifs from known SHIP2 inhibitors were synthesized and evaluated for SHIP2-inhibiting activity against a recombinant SHIP2 protein in vitro. Three aurones that inhibited SHIP2 at 15-50 μM were identified. These aurone inhibitors required two amine functionalities, one at ring A and a second at ring B for good inhibitory activity as exemplified by 12a. Mechanistically, molecular dynamics simulations revealed 12a to preferably bind to an allosteric site, restricting the motion of the flexible L4 loop required for SHIP2 phosphatase activity. Additionally, a basic piperidine moiety of 12a interacted with an aspartate residue proximal to the site. At 20-40 μM, 12a significantly enhanced glucose uptake in rat myotubes via increased Akt phosphorylation. 12a showed good permeability across the Caco-2 cell monolayer supporting the aurone chemotype as a new lead to develop drug-like, oral insulin sensitizers.

C-terminal peptide of preproorexin enhances brain-derived neurotrophic factor expression in rat cerebrocortical cells and recognition memory in mice

During the production of orexin A and B from preproorexin, a common precursor protein, in hypothalamic orexin neurons, C-terminal peptide (herein called preproorexin C-peptide) is concomitantly produced via post-translational processing. The predicted three-dimensional structure of preproorexin C-peptide is similar among mammalian species, suggestive of a conserved function in the mammalian brain. However, C-peptide has long been regarded as a non-functional peptide. We herein examined the effects of rat and/or mouse preproorexin C-peptide on gene expression and cell viability in cultured rat cerebrocortical cells and on memory behavior in C57BL/6J mice. Rat and mouse C-peptides both increased brain-derived neurotrophic factor (Bdnf) mRNA levels. Moreover, C-peptide enhanced high K+-, glutamate-, and BDNF-induced increases in Bdnf mRNA levels without affecting forskolin-induced Bdnf expression. H-89, a protein kinase A inhibitor, blocked C-peptide-induced Bdnf expression, whereas rolipram, a phosphodiesterase inhibitor, enhanced this effect. Intracellular cyclic AMP concentrations were elevated by C-peptide. These results demonstrate that preproorexin C-peptide promoted Bdnf mRNA expression by a cyclic AMP-dependent mechanism. Eleven amino acids at the N terminus of rat preproorexin C-peptide exerted similar effects on Bdnf expression as full-length preproorexin C-peptide. Preproorexin C-peptide also exerted protective effects against CoCl2-induced neuronal cell death. An intracerebroventricular injection of mouse preproorexin C-peptide induced c-fos and Bdnf expression in the cerebral cortex and hippocampus and enhanced novel object recognition memory in mice. Collectively, the present results show that preproorexin C-peptide is a functional substance, at least in some pharmacological and neuronal settings.

Small molecule targeting of SHIP1 and SHIP2

Modulating the activity of the Src Homology 2 (SH2) — containing Inositol 5′-Phosphatase (SHIP) enzyme family with small molecule inhibitors provides a useful and unconventional method of influencing cell signaling in the PI3K pathway. The development of small molecules that selectively target one of the SHIP paralogs (SHIP1 or SHIP2) as well as inhibitors that simultaneously target both enzymes have provided promising data linking the phosphatase activity of the SHIP enzymes to disorders and disease states that are in dire need of new therapeutic targets. These include cancer, immunotherapy, diabetes, obesity, and Alzheimer's disease. In this mini-review, we will provide a brief overview of research in these areas that support targeting SHIP1, SHIP2 or both enzymes for therapeutic purposes.