Targeting of Protein Phosphatases PP2A and PP2B to the C-Terminus of the L-Type Calcium Channel Ca_v1.2

The L-type Ca2+ channel Cav1.2 forms macromolecular signaling complexes that comprise the β2 adrenergic receptor, trimeric Gs protein, adenylyl cyclase, and cAMP-dependent protein kinase (PKA) for efficient signaling in heart and brain. The protein phosphatases PP2A and PP2B are part of this complex. PP2A counteracts increase in Cav1.2 channel activity by PKA and other protein kinases, whereas PP2B can either augment or decrease Cav1.2 currents in cardiomyocytes depending on the precise experimental conditions. We found that PP2A binds to two regions in the C-terminus of the central, pore-forming α1 subunit of Cav1.2: one region spans residues 1795−1818 and the other residues 1965−1971. PP2B binds immediately downstream of residue 1971. Injection of a peptide that contained residues 1965−1971 and displaced PP2A but not PP2B from endogenous Cav1.2 increased basal and isoproterenol-stimulated L-type Ca2+ currents in acutely isolated cardiomyocytes. Together with our biochemical data, these physiological results indicate that anchoring of PP2A at this site of Cav1.2 in the heart negatively regulates cardiac L-type currents, likely by counterbalancing basal and stimulated phosphorylation that is mediated by PKA and possibly other kinases

Diagnostic Microdosing Approach to Study Gemcitabine Resistance

Gemcitabine metabolites cause the termination of DNA replication and induction of apoptosis. We determined whether subtherapeutic “microdoses” of gemcitabine are incorporated into DNA at levels that correlate to drug cytotoxicity. A pair of nearly isogenic bladder cancer cell lines differing in resistance to several chemotherapy drugs were treated with various concentrations of ¹⁴C-labeled gemcitabine for 4–24 h. Drug incorporation into DNA was determined by accelerator mass spectrometry. A mechanistic analysis determined that RRM2, a DNA synthesis protein and a known resistance factor, substantially mediated gemcitabine toxicity. These results support gemcitabine levels in DNA as a potential biomarker of drug cytotoxicity

Supplementary Figure S1 from Oxaliplatin–DNA Adducts as Predictive Biomarkers of FOLFOX Response in Colorectal Cancer: A Potential Treatment Optimization Strategy

Supplementary Figure S1 showing correlation between CRC cell line oxaliplatin sensitivity and oxaliplatin-DNA area under the adduct curve</p

Figure S1 from COX-2/sEH Dual Inhibitor PTUPB Potentiates the Antitumor Efficacy of Cisplatin

PTUPB structure</p

Supplementary Figure Legends from COX-2/sEH Dual Inhibitor PTUPB Potentiates the Antitumor Efficacy of Cisplatin

Supplementary Figure Legends</p

Figure S7 from COX-2/sEH Dual Inhibitor PTUPB Potentiates the Antitumor Efficacy of Cisplatin

PTUPB did not increase cisplatin cytotoxicity in the J82, T24 and TCCSUP bladder cancer cell lines</p

Figure S3 from COX-2/sEH Dual Inhibitor PTUPB Potentiates the Antitumor Efficacy of Cisplatin

Body weight change during PDX bladder cancer mice experiment</p

DNA damage as the critical step in Pt-induced cell death.

<p>(A) The major pathways of platinum (Pt) drug-induced cell death. After administration, cellular uptake and efflux determines the intracellular accumulation of Pt agents, which can be inactivated by the intracellular thiol-containing molecules. Eventually, Pt agents induce DNA damage, including drug-DNA adducts, which triggers cell cycle arrest and DNA repair. DNA adduct formation and repair determines the fate of cells, although other factors also play important roles, such as pro- and anti-apoptotic proteins. (B) Diagram showing the formation of carboplatin- and oxaliplatin-DNA adducts and the positions of the radiocarbon labels on each drug used for this study in order to enable quantification of drug-DNA adduct formation and repair by accelerator mass spectrometry.</p

Table S1 from COX-2/sEH Dual Inhibitor PTUPB Potentiates the Antitumor Efficacy of Cisplatin

LC-MS/MS analysis of lipid metabolites in PDX BL0269</p