Biology subjects

Au, C. C.

Publications and source records attributed to Au, C. C..

4 recordsLinked to original sources

bioRxiv2026

AR-V7 Utilizes a Noncanonical Nuclear Localization Signal to Sustain Androgen-Independent Nuclear Import and Signaling

AR-V7 is the most prevalent androgen receptor splice variant in metastatic castration-resistant prostate cancer, yet how it enters the nucleus independently of androgen binding has remained unclear. We previously demonstrated that AR-V7 undergoes nuclear import via a non-canonical pathway distinct from the microtubule-based, importin-/{beta}- and Ran-dependent mechanism used by full-length AR. Here, using systematic truncation and alanine-scanning mutagenesis, we identify a non-classical nuclear localization motif at the junction of the DNA-binding domain (DBD) and cryptic exon 3 (CE3) that is required for efficient AR-V7 nuclear import. Specific basic residues within the DBD and CE3 are required not only for nuclear entry but also for transcriptional activity. Unexpectedly, mutants retaining partial nuclear localization were transcriptionally silent, suggesting that CE3 contributes to transcriptional engagement through mechanisms separate from nuclear transport. Genome-wide transcriptomic analysis of a strongly import-deficient mutant confirmed that disruption of nuclear entry abolishes the AR-V7 transcriptional program. To map compartment-specific protein interactions, we applied antibody-guided photocatalytic proximity labeling. Nuclear AR-V7 associated most prominently with both canonical BAF and PBAF SWI/SNF chromatin remodeling complexes, together with known transcriptional coregulators and DNA-repair factors, whereas the cytoplasm-restricted mutant engaged different networks centered on mRNA deadenylation and decay, cytoskeletal regulation, and chaperone systems. Together, these findings define a variant-specific NLS, separate nuclear import from CE3-dependent transcriptional competence, and identify the cytoplasmic networks that become accessible when AR-V7 nuclear entry is impaired. They reveal two mechanistically distinct vulnerabilities for suppressing AR-V7 signaling: blocking nuclear translocation and disrupting CE3-dependent transcriptional engagement within the nucleus.

cancer biology↗

bioRxiv2024

The Orphan G Protein-Coupled Receptor GPR52 is a Novel Regulator of Breast Cancer Multicellular Organization

Statement of SignificanceWe showed that loss of the orphan G protein-coupled receptor GPR52 in human breast cell lines leads to increased cell clustering, hybrid/partial EMT, and increased tumor burden in zebrafish. BackgroundG protein-coupled receptors (GPCRs) are the largest class of membrane-bound receptors that transmit critical signals from extracellular to intracellular spaces. Transcriptomic data of resected breast tumors show that low mRNA expression of orphan GPCR GPR52 correlates with reduced overall survival in patients with breast cancer, leading to the hypothesis that loss of GPR52 supports breast cancer progression. MethodsCRISPR-Cas9 was used to knockout GPR52 in the human triple-negative breast cancer (TNBC) cell lines MDA-MB-468 and MDA-MB-231, and in the non-cancerous breast epithelial cell line MCF10A. 2D and 3D in vitro studies, electron microscopy, Matrigel culture, and a zebrafish xenograft model were used to assess the morphology and behavior of GPR52 KO cells. RNA-sequencing and proteomic analyses were also conducted on these cell lines, and transcriptomic data from The Cancer Genome Atlas (TCGA) database were used to compare GPR52-null and wild-type (WT) signatures in breast cancer. ResultsLoss of GPR52 was found to be associated with increased cell-cell interaction in 2D cultures, altered 3D spheroid morphology, and increased propensity to organize and invade collectively in Matrigel. Furthermore, GPR52 loss was associated with features of EMT in MDA-MB-468 cells, and zebrafish injected with GPR52 KO cells developed a greater total cancer area than those injected with control cells. RNA sequencing and proteomic analyses of GPR52-null breast cancer cells revealed an increased cAMP signaling signature. Consistently, we found that treatment of wild-type (WT) cells with forskolin, which stimulates the production of cAMP, induces phenotypic changes associated with GPR52 loss, and inhibition of cAMP production rescued some GPR52 KO phenotypes. ConclusionGPR52 is an orphan GPCR and its role in cancer progression has not been previously characterized. We found that GPR52 loss in breast cancer cells can lead to increased cell clustering, collective invasion, and EMT in vitro. These are features of increased cancer aggression. Our results reveal that GPR52 loss is a potential mechanism by which breast cancer progression may occur and support the investigation of GPR52 agonism as a therapeutic option for breast cancer. O_FIG O_LINKSMALLFIG WIDTH=169 HEIGHT=200 SRC="FIGDIR/small/604482v2_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@8b0f55org.highwire.dtl.DTLVardef@19bd139org.highwire.dtl.DTLVardef@c52117org.highwire.dtl.DTLVardef@1ffa2bd_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG

cancer biology↗

bioRxiv2021

AR-V7 exhibits non-canonical mechanisms of nuclear import and chromatin engagement in Castrate-Resistant Prostate Cancer

Expression of the AR splice variant, AR-V7, in prostate cancer is correlated with poor patient survival and resistance to AR targeted therapies and taxanes. Currently, there is no specific inhibitor of AR-V7, while the molecular mechanisms regulating its biological function are not well elucidated. Here we report that AR-V7 has unique biological features that functionally differentiate it from canonical AR-fl or from the second most prevalent variant, AR-v567. First, AR-V7 exhibits fast nuclear import kinetics via a pathway distinct from the nuclear localization signal dependent importin- /{beta} pathway used by AR-fl and AR-v567. We also show that the dimerization box domain, known to mediate AR dimerization and transactivation, is required for AR-V7 nuclear import but not for AR-fl. Once in the nucleus, AR-V7 is transcriptionally active, yet exhibits unusually high intranuclear mobility and transient chromatin interactions, unlike the stable chromatin association of liganded AR-fl. The high intranuclear mobility of AR-V7 together with its high transcriptional output, suggest a Hit-and-Run mode of transcription. Our findings reveal unique mechanisms regulating AR-V7 activity, offering the opportunity to develop selective therapeutic interventions.

cancer biology↗

bioRxiv2020

Unacylated ghrelin and AZP531 suppress the 3D growth of breast cancers

Breast cancer is the most common type of cancer in women and notwithstanding important therapeutic advances, it remains the second leading cause of cancer-related death in the US. Despite extensive research relating to the hormone ghrelin, responsible for the stimulation of growth hormone release and appetite, little is known of the effects of its unacylated form, especially in cancer. One major area of research relates to its reported effects to increase insulin sensitivity in diabetics, this being the basis for the development of unacylated ghrelin analog, AZP531 or livoletide, now in clinical trials for the treatment of Prader-Willi Syndrome. The mechanism of action of unacylated ghrelin is largely uncharacterized, in any system, because it does not bind to or activate the cognate ghrelin receptor, GHSR1a. The present study aimed to characterize effects of unacylated ghrelin on breast cancer cells, define its mechanism of action, and explore the therapeutic potential of unacylated ghrelin or analog AZP531. We report potent effects of unacylated ghrelin, at picomolar doses, on the growth of breast cancer cells, dependent on 3D culture and activation of Gi. Suppression of MAPK signaling by unacylated ghrelin leads to cell cycle arrest and apoptosis. AZP531 also suppresses the growth of breast cancer cells in vitro and in xenografts, and may be a novel approach for the safe and effective treatment of breast cancer.

cancer biology↗