Phosphoinositide 3-kinaseγ (PI3Kγ) is activated by G-protein coupled receptors (GPCRs). We show here that PI3Kγ inhibits protein phosphatase 2A (PP2A) at the β-adrenergic receptor (βAR, a GPCR) complex altering G-protein coupling. PI3Kγ inhibition results in significant increase of βAR-associated phosphatase activity leading to receptor dephosphorylation and resensitization preserving cardiac function. Mechanistically, PI3Kγ inhibits PP2A activity at the βAR complex by phosphorylating an intracellular inhibitor of PP2A (I2PP2A) on serine residues 9 & 93 resulting in enhanced binding to PP2A. Indeed, enhanced phosphorylation of β2ARs is observed with phosphomimetic I2PP2A mutant that was completely reversed with a mutant mimicking dephosphorylated state. siRNA depletion of endogenous I2PP2A augments PP2A activity despite active PI3K resulting in β2AR dephosphorylation and sustained signaling. Our study provides the underpinnings of a PI3Kγ mediated regulation of PP2A activity that has significant consequences on receptor function with broad implications in cellular signaling.

Curcumin, the primary active ingredient in the spice turmeric, was converted to reactive monofunctional derivatives (carboxylic acid/azide/alkyne). The derivatives were employed to produce a 3 + 2 azide-alkyne "clicked" curcumin dimer and a poly(amidoamine) (PAMAM) dendrimer-curcumin conjugate. The monofunctional curcumin derivatives retain biological activity and are efficient for labeling and dissolving amyloid fibrils. The curcumin dimer selectively destroys human neurotumor cells. The synthetic methodology developed affords a general strategy for attaching curcumin to various macromolecular scaffolds.

In this study we demonstrate that treatment with anti-CD40 mAb eradicates a range of mouse lymphomas (BCL1, A31, A20, and EL4), but only when used against i.v. tumor doses in excess of 107 cells. Only partial protection was seen against smaller tumor loads. We saw no evidence that anti-CD40 mAb changed the phenotype of the lymphomas or inhibited their growth in the initial period following treatment, but it did result in a rapid expansion of cytotoxic CD8+ cells that was able to clear the neoplastic disease and provide long-term protection against tumor rechallenge. The CTL responses were blocked by mAb against a range of coreceptors and cytokines, including CD8, B7-1, B7-2, LFA-1, and IFN-γ, but not CD4 or CTLA-4, indicating the presence of a conventional cellular Th1 response. Furthermore, we found evidence of cross-recognition between lymphomas (BCL1 and A20) as measured by cytotoxicity and IFN-γ responses in vitro and using tumor rechallenge experiments, suggesting common target Ags. Finally, although anti-CD40 was shown to stimulate NK cell killing, we could find no role for these cells in controlling tumor growth. These data underline the ability of anti-CD40 mAb to potentiate CTL responses and the potency of cellular immunity in eradicating large quantities of syngeneic tumor.