Mouse Model for Protein Tyrosine Phosphatase D (PTPRD) Associations with Restless Leg Syndrome or Willis-Ekbom Disease and Addiction: Reduced Expression Alters Locomotion, Sleep Behaviors and Cocaine-Conditioned Place Preference.

The receptor type protein tyrosine phosphatase D (PTPRD) gene encodes a cell adhesion molecule likely to influence development and connections of addiction-, locomotion- and sleep-related brain circuits in which it is expressed. The PTPRD gene harbors genome-wide association signals in studies of restless leg syndrome (Willis-Ekbom disease [WED]/restless leg syndrome [RLS]; p < 10-8) and addiction-related phenotypes (clusters of nearby single nucleotide polymorphisms [SNPs] with 10-2 > p > 10-8 associations in several reports). We now report work that seeks (a) association between PTPRD genotypes and expression of its mRNA in postmortem human brains and (b) RLS-related, addiction-related and comparison behavioral phenotypes in hetero- and homozygous PTPRD knockout mice. We identify associations between PTPRD SNPs and levels of PTPRD mRNA in human brain samples that support validity of mouse models with altered PTPRD expression. Knockouts display less behaviorally defined sleep at the end of their active periods. Heterozygotes move more despite motor weakness/impersistence. Heterozygotes display shifted dose-response relationships for cocaine reward. They display greater preference for places paired with 5 mg/kg cocaine and less preference for places paired with 10 or 20 mg/kg. The combined data provide support for roles for common, level-of-expression PTPRD variation in locomotor, sleep and drug reward phenotypes relevant to RLS and addiction. Taken together, mouse and human results identify PTPRD as a novel therapeutic target for RLS and addiction phenotypes.

Inhibition of Karyopherin beta 1 suppresses prostate cancer growth.

Prostate cancer (PCa) initiation and progression requires activation of numerous oncogenic signaling pathways. Nuclear-cytoplasmic transport of oncogenic factors is mediated by Karyopherin proteins during cell transformation. However, the role of nuclear transporter proteins in PCa progression has not been well defined. Here, we report that the KPNB1, a key member of Karyopherin beta subunits, is highly expressed in advanced prostate cancers. Further study showed that targeting KPNB1 suppressed the proliferation of prostate cancer cells. The knockdown of KPNB1 reduced nuclear translocation of c-Myc, the expression of downstream cell cycle modulators, and phosphorylation of regulator of chromatin condensation 1 (RCC1), a key protein for spindle assembly during mitosis. Meanwhile, CHIP assay demonstrated the binding of c-Myc to KPNB1 promoter region, which indicated a positive feedback regulation of KPNB1 expression mediated by the c-Myc. In addition, NF-κB subunit p50 translocation to nuclei was blocked by KPNB1 inhibition, which led to an increase in apoptosis and a decrease in tumor sphere formation of PCa cells. Furthermore, subcutaneous xenograft tumor models with a stable knockdown of KPNB1 in C42B PCa cells validated that the inhibition of KPNB1 could suppress the growth of prostate tumor in vivo. Moreover, the intravenously administration of importazole, a specific inhibitor for KPNB1, effectively reduced PCa tumor size and weight in mice inoculated with PC3 PCa cells. In summary, our data established the functional link between KPNB1 and PCa prone c-Myc, NF-kB, and cell cycle modulators. More importantly, inhibition of KPNB1 could be a new therapeutic target for PCa treatment.

Sequence- and structure-based computational analyses of Gram-negative tripartite efflux pumps in the context of bacterial membranes.

Gram-negative multidrug resistance currently presents a serious threat to public health with infections effectively rendered untreatable. Multiple molecular mechanisms exist that cause antibiotic resistance and in addition, the last three decades have seen slowing rates of new drug development. In this review, we summarize the use of various computational techniques for investigating the mechanisms of multidrug resistance mediated by Gram-negative tripartite efflux pumps and membranes. Recent work in our lab combines data-driven sequence and structure analyses to study the interactions and dynamics of these bacterial components. Computational studies can complement experimental methodologies for gaining crucial insights into combatting multidrug resistance.

Mechanisms of Adipocytokine-Mediated Trastuzumab Resistance in HER2-Positive Breast Cancer Cell Lines.

Acquired resistance to trastuzumab is a clinical problem in the treatment of HER2-over-expressing metastatic breast cancer. Importantly, an earlier report suggested that high body mass index was associated with reduced overall survival and reduced time to progression in patients with early stage or metastatic HER2-positive breast cancer treated with trastuzumab. Adipocyte-secreted factors may stimulate growth of HER2-positive cancers, blocking the growth inhibitory action of trastuzumab. Leptin and growth differentiation factor 15 (GDF15) are two adipocytokines that have been reported to stimulate HER2-PI3K signaling. We previously showed that cells with acquired trastuzumab resistance express increased levels of GDF15, and that GDF15 knockdown restores sensitivity to trastuzumab. The objective of the current study was to identify potential molecular mechanisms by which adipocytes stimulate resistance to trastuzumab in HER2-over-expressing breast cancer cell lines. Cells were cultured in complete media or conditioned media from differentiated adipocytes (CM). Cell viability of trastuzumab-treated cells was examined under anchorage-dependent and -independent conditions. Phosphorylation of Akt was assessed by Western blotting, and response to trastuzumab was reassessed upon treatment with the PI3K inhibitor LY294002 or after transfection with kinase-dead Akt. We report that CM significantly reduced trastuzumab-mediated growth inhibition of HER2-positive cells, and stimulated rapid phosphorylation of Akt. Pharmacologic or genetic inhibition of PI3K overcame CM-mediated trastuzumab resistance. Leptin and GDF15 were both measured in CM, but only GDF15 conferred resistance to trastuzumab. Leptin, on the other hand, abrogated sensitivity to lapatinib but not trastuzumab. Our observations suggest that adipocyte-secreted factors such as GDF15 stimulate PI3K signaling, resulting in reduced response to trastuzumab. The utility of adipocytokines as predictors of drug resistance and approaches to mitigate the cancer-promoting effects of adipocyte-secreted factors should be further examined. Our work supports additional investigation into GDF15 as a potential biomarker of trastuzumab resistance, and development of approaches to therapeutically target GDF15 in HER2-positive breast cancers that have progressed on trastuzumab.