Overexpression Of PAQR3 Research Articles

PAQR3 facilitates the ferroptosis of diffuse large B-cell lymphoma via the regulation of LDLR-mediated PI3K/AKT pathway.

Progesterone and adiponectin receptor 3 (PAQR3) has been found to regulate tumor progression by mediating cell ferroptosis. However, whether PAQR3 mediates ferroptosis in diffuse large B-cell lymphoma (DLBCL) needs further investigation. The mRNA and protein levels of PAQR3 and low-density lipoprotein receptor (LDLR) were assessed by qRT-PCR and WB assays. Cell proliferation was detected by MTT assay and EdU assay. Shrunken mitochondria was counted under transmission electron microscope. Cell ferroptosis was evaluated by measuring the levels of malondialdehyde, reactive oxygen species, glutathione, Fe2+ , and the protein expression of ferroptosis-related markers. PAQR3 and LDLR interaction was confirmed by RIP assay and pull-down assay. Our study showed that PAQR3 was underexpressed, while LDLR was overexpressed in DLBCL tissues and cells. Functionally, PAQR3 overexpression or LDLR knockdown restrained DLBCL cell proliferation and enhanced ferroptosis. Mechanistically, PAQR3 reduced LDLR expression by inhibiting its mRNA stability. Meanwhile, LDLR overexpression reversed PAQR3-mediated the promoting on DLBCL cell ferroptosis, and LY294002 (PI3K/AKT inhibitor) eliminated the inhibiting effects of LDLR overexpression on DLBCL cell ferroptosis. Additionally, excessive PAQR3 reduced DLBCL tumor growth by enhancing tumor cell ferroptosis through LDLR-mediated PI3K/AKT pathway. In conclusion, our data suggested that PAQR3 restrained DLBCL progression by aggravating ferroptosis, which was achieved by inhibiting LDLR expression to repress PI3K/AKT pathway.

Golgi scaffold protein PAQR3 as a candidate suppressor of gastric cardia adenocarcinoma via regulating TGF-β/Smad pathway.

ObjectivesTo investigate the function of PAQR3 in gastric cardia adenocarcinoma (GCA) and understand the possible mechanism of PAQR3 in regulating epithelial–mesenchymal transition (EMT).MethodsWe detected PAQR3 protein in 146 GCA tissues and paired normal adjacent tissues (PNTs) specimens using immunohistochemical analysis, and explored its clinical significance. The expression levels of PAQR3 protein in 20 GCA tissues, their paired PNTs, HGC27, SGC7901, and GES‐1 cells were analyzed by Western blot. Wild‐type PAQR3 was overexpressed in HGC27 cells. The effects of PAQR3 overexpression on the function of HGC27 cells and its underlying mechanisms were then analyzed through a series of cell and molecular biology experiments.ResultsPAQR3 was significantly down‐regulated in GCA tissues when compared with paired PNTs (p < 0.0001). The expression level of PAQR3 in GCA tissues was significantly negatively correlated with Helicobacter pylori infection (p = 0.000), venous invasion (p = 0.000), invasion depth (p = 0.000), lymph node metastasis (p = 0.022), tumor stage (p = 0.000), and patient survival (p = 0.009). Downregulation of PAQR3 was highly correlated with increased EMT signature and activated TGF‐β/Smad pathway in GCA tissues. Overexpression of PAQR3 in HGC27 cells negatively regulates its cellular functions, such as cell proliferation and migration, and suppresses EMT. Mechanistically, overexpression of PAQR3 significantly down‐regulates the protein expression levels of TGF‐1, p‐Smad2, and p‐Smad3 in HGC27 cells.ConclusionPAQR3 was significantly down‐regulated in GCA tissues, HGC27, and SGC7901 cells. PAQR3 significantly inhibits the proliferation, migration, and invasion of HGC27 cells. Mechanistically, PAQR3 can inhibit the EMT process in HGC27 cells by regulating TGF‐β/Smad signaling pathway.

Exosomes from linc00511-overexpressing ADSCs accelerates angiogenesis in diabetic foot ulcers healing by suppressing PAQR3-induced Twist1 degradation

AimsWe aim to investigate the role of ADSCs (Adipose-derived stem cells)-derived exosomes on regulating angiogenesis in diabetic foot ulcers healing. MethodsEPCs (endothelial progenitor cells) from human peripheral blood were applied as in vitro model of angiogenesis. Exosomes isolated from ADSCs culture medium were characterized by electron microscopy, size distribution and biomarker expression. Cell proliferation, migration, apoptosis and angiogenesis were detected by CCK-8 and EdU staining, wound healing, flow cytometry and tube formation assays, respectively. Rat diabetic foot model was further constructed for the evaluation of wound healing and histological alterations. ResultsEPCs from diabetes showed suppressed proliferation, migration and angiogenesis and decreased Twist1 protein. Similarly, high glucose repressed the proliferation, migration and angiogenesis of EPCs, which also elevated PAQR3 and suppressed Twist1 expression. However, these impaired EPCs biological functions were recovered by the application of exosomes from linc00511-overexpressing ADSCs, along with increased Twist1 and decreased PAQR3. Mechanistically, PAQR3 overexpression reduced Twist1 protein level in EPCs by enhancing BTRC-mediated Twist1 ubiquitin degradation. Exosomes from linc00511-overexpressing ADSCs alleviated rat diabetic foot ulcers by inhibiting Twist1 ubiquitination to promote angiogenesis. ConclusionExosomes from linc00511-overexpressing ADSCs promotes diabetic foot ulcers healing by accelerating angiogenesis via suppressing PAQR3-induced Twist1 ubiquitin degradation.

Exosomes from linc00511-Overexpressing ADSCs Accelerates Angiogenesis in Diabetic Foot Ulcers Healing by Suppressing of PAQR3-Induced Twist1 Degradation

Background: Exosomes from ADSCs (adipose-derived stem cells) possess various therapeutic effects, but their roles in diabetic foot ulcers are poorly understood. We aimed to investigate the role of ADSCs-derived exosomes on regulating angiogenesis in diabetic foot ulcers healing. Methods: EPCs (endothelial progenitor cells) from human peripheral blood were applied as in vitro model of angiogenesis. Exosomes isolated from ADSCs culture medium were characterized by electron microscopy, size distribution and biomarker expression. Cell proliferation, migration, apoptosis and angiogenesis were detected by CCK-8 and EdU staining, wound healing, flow cytometry and tube formation assays, respectively. Expression of inflammatory factors and related genes in serum and cell culture or tissues were detected by ELISA, IF, qRT-PCR and western blotting as appropriate. The PAQR3-BTRC-Twist1 interaction was verified using Co-immunoprecipitation. Rat diabetic foot model was further constructed for the evaluation of wound healing and histological alterations. Findings: EPCs from diabetes showed suppressed proliferation, migration and angiogenesis and decreased Twist1 protein. Similarly, high glucose repressed the proliferation, migration and angiogenesis of EPCs, which also elevated PAQR3 and suppressed Twist1 expression. However, these impaired EPCs biological functions were recovered by the application of exosomes from linc00511-overexpressing ADSCs, along with increased Twist1 and decreased PAQR3. Mechanistically, PAQR3 overexpression reduced Twist1 protein level in EPCs by enhancing BTRC-mediated Twist1 ubiquitin degradation. Exosomes from linc00511-overexpressing ADSCs alleviated rat diabetic foot ulcers by inhibiting Twist1 ubiquitination to promote angiogenesis. Interpretation: Exosomes from linc00511-overexpressing ADSCs promotes diabetic foot ulcers healing by accelerating angiogenesis via suppressing PAQR3-induced Twist1 ubiquitin degradation. Funding Statement: None. Declaration of Interests: The authors declare that there is no conflict of interest. Ethics Approval Statement: The study with human blood samples were approved by the Ethics Committee of Central South University (Changsha, China). Written informed consents were obtained from all DM patients and volunteers before blood sample collection. Above animal operations were approved by the Research Animal Ethics Committee of Central South University and carried out following the Guide for the Care and Use of Laboratory Animals (NIH).

PAQR3 protects against oxygen-glucose deprivation/reperfusion-induced injury through the ERK signaling pathway in N2A cells.

Cerebral ischemia-reperfusion injury is pivotal in the development of multiple-subcellular organelle and tissue injury after acute ischemic stroke. Recently, the Golgi apparatus (GA) has been shown to be a key subcellular organelle that plays an important role in neuroprotection against oxygen-glucose deprivation/reperfusion (OGD/R) injury. PAQR3, a scaffold protein exclusively localized in the GA, was originally discovered as a potential tumor suppressor protein. PAQR3 acts as a spatial regulator of Raf-1 that binds Raf-1 and sequesters it to the GA, where it negatively modulates the Ras/Raf/MEK/ERK signaling pathway in tumor models. Studies suggest that suppression of the ERK pathway can alleviate OGD/R-induced cell apoptosis. However, whether PAQR3 has potential effects on ischemic stroke and the underlying mechanism(s) remain unexplored. The current study is the first to show that PAQR3 was significantly downregulated in mouse neuroblastoma (N2A) cells upon OGD/R exposure, both at the mRNA and protein levels. Compared to that in controls, the mRNA level of PAQR3 began to decline at 0h (0h) after reperfusion, while the protein level began to decline at 4h. Furthermore, overexpression of PAQR3 reduced OGD/R-induced apoptosis. The mRNA and protein levels of total ERK1 and ERK2 were unaltered, while activated p-ERK1 and p-ERK2 were decreased in N2A cells transfected with a PAQR3 expression vector after OGD for 4h plus 24h of reperfusion. Collectively, these data indicated that increased PAQR3 expression protected against OGD/R-induced apoptosis possibly by inhibiting the ERK signaling pathway. Therefore, PAQR3 might be a new attractive target in the treatment of OGD/R insult, and the underlying mechanism will pave the way for its potential experimental and clinical application.

PAQR3 modulates blood cholesterol level by facilitating interaction between LDLR and PCSK9

ObjectiveLow-density lipoprotein cholesterol (LDL-C) is the hallmark of atherosclerotic cardiovascular diseases. The hepatic LDL receptor (LDLR) plays an important role in clearance of circulating LDL-C. PCSK9 facilitates degradation of LDLR in the lysosome and antagonizing PCSK9 has been successfully used in the clinic to reduce blood LDL-C level. Here we identify a new player that modulates LDLR interaction with PCSK9, thus controlling LDLR degradation and cholesterol homeostasis. MethodsThe blood LDL-C and cholesterol levels were analyzed in mice with hepatic deletion of Paqr3 gene. The half-life of LDLR was analyzed in HepG2 cells. The interaction of PAQR3 with LDLR and PCSK9 was analyzed by co-immunoprecipitation and immunofluorescent staining. ResultsThe blood LDL-C and total cholesterol levels in the mice with hepatic deletion of Paqr3 gene were significantly lower than the control mice after feeding with high-fat diet (p < 0.001 and p < 0.05 respectively). The steady-state level of LDLR protein is elevated by Paqr3 knockdown/deletion and reduced by PAQR3 overexpression. The half-life of LDLR protein is increased by Paqr3 knockdown and accelerated by PAQR3 overexpression. PAQR3 interacts with the β-sheet domain of LDLR and the P-domain of PCSK9 respectively. In addition, PAQR3 can be localized in early endosomes and colocalized with LDLR, PCSK9 and LDL. Mechanistically, PAQR3 enhances the interaction between LDLR and PCSK9. ConclusionOur study reveals that PAQR3 plays a pivotal role in controlling hepatic LDLR degradation and blood LDL-C level via modulating LDLR-PCSK9 interaction.

PAQR3 inhibits proliferation via suppressing PI3K/AKT signaling pathway in non-small cell lung cancer.

IntroductionLung cancer is the leading cause of cancer-related death worldwide and non-small cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancer cases. PAQR (progestin and adipoQ receptor family) 3, a Golgi-anchored membrane protein, has been demonstrated to act as a tumor suppressor in multiple cancers. However, the expression and role of PAQR3 have never been explored in NSCLC. The purpose of this study was to investigate the expression and role of PAQR3 in NSCLC.Material and methodsExpression of PAQR3 at mRNA and protein levels was determined by qRT-PCR and western blot, respectively. Cell proliferation was analyzed by MTT assay. Apoptosis and cell cycle distribution were evaluated by flow cytometry.ResultsThe expression of PAQR3 was downregulated in NSCLC tissue samples and cell lines at both mRNA and protein levels (p < 0.05). Overexpression of PAQR3 significantly inhibited cell proliferation, induced apoptosis and promoted cell cycle arrest at G0/G1 phase in NSCLC cell lines (p < 0.05). In contrast, knockdown of PAQR3 showed a reverse effect on NSCLC cells (p < 0.05). Moreover, PAQR3 may exert its tumor suppressive roles via suppressing the PI3K/AKT signaling pathway in NSCLC.ConclusionsOur findings suggest that PAQR3 is a tumor suppressor in the development of NSCLC and may serve as a novel therapeutic target in the treatment of patients with NSCLC.

PAQR3 Inhibits the Proliferation and Tumorigenesis in Esophageal Cancer Cells.

Progestin and adipoQ receptor family member III (PAQR3), a member of the PAQR family, is frequently downregulated in different types of human cancer. However, its expression and functions in esophageal cancer are still unknown. This study aimed to explore the expression of PAQR3 in esophageal cancer cell lines and to investigate the role of PAQR3 in the development of esophageal cancer. Our data showed that PAQR3 is expressed in low amounts in human esophageal cancer cell lines. Overexpression of PAQR3 significantly suppressed the proliferation, migration, and invasion of esophageal cancer cells. In addition, overexpression of PAQR3 downregulated the protein expression levels of RAF1, p-MEK1, and p-ERK1/2 in esophageal cancer cells. Furthermore, overexpression of PAQR3 attenuated the tumor growth in a tumor xenograft model. In conclusion, we demonstrated that overexpression of PAQR3 suppresses cell proliferation, migration, and invasion in esophageal cancer in vitro and in vivo. Therefore, PAQR3 may act as a therapeutic target for human esophageal cancer.

Subcellular distribution of RAD23B controls XPC degradation and DNA damage repair in response to chemotherapy drugs

The RAD23B-XPC complex in the nucleus plays a key role in the initial damage recognition during global genome nucleotide excision repair (NER). Within the complex, XPC, a product of Xeroderma pigmentosum C, recognizes and interacts with the unpaired bases in the undamaged DNA strand, while RAD23B stabilizes XPC. However, how RAD23B is regulated by other factors is not well known. We report here a mode of spatial regulation of RAD23B that controls XPC stability and DNA damage repair. We first identified that RAD23B was able to directly associate with PAQR3, a newly-discovered tumor suppressor implicated in many types of human cancers. PAQR3 reduced the protein level of XPC, together with accelerated degradation and enhanced polyubiquitination of XPC. Mechanistically, PAQR3 reduces nucleic distribution of RAD23B by tethering it to the Golgi apparatus, thus diminishing the amount of RAD23B proteins available to interact with XPC in the nucleus. The viability of gastric cancer cells upon treatment with chemotherapy drugs including etoposide, cisplatin and doxorubicin was reduced by PAQR3 overexpression, but enhanced by PAQR3 knockdown. The degree of DNA damage induced by these drugs, as measured by immunoblotting with γ-H2AX, was elevated by PAQR3 overexpression and lessened by PAQR3 knockdown. Furthermore, a synthetic peptide comprising the N-terminus of PAQR3 was able to recapitulate the activity of PAQR3 in reducing XPC stability and enhancing chemotherapy drug-induced DNA damage. In conclusion, our study reveals that RAD23B is controlled by subcellular compartmentation, thus affecting XPC-mediated DNA damage repair in cancer cells.

The role of PAQR3 gene promoter hypermethylation in breast cancer and prognosis.

PAQR3 is a tumor suppressor in breast cancer and its expression regulation mechanism has not been well elucidated. In this study, we found that PAQR3 expression was downregulated in breast cancer tissues, and the downregulation of PAQR3 expression was found to be significantly associated with aberrant methylation of the gene promoter. Methylation‑specific PCR showed that hypermethylation of the PAQR3 gene was observed in 71.8% of the breast cancers, whereas it was found in only 28.2% of the corresponding non‑tumor tissues. Moreover, we found that the PAQR3 promoter methylation status was related to lymph node metastasis (P=0.01). In addition, overexpression of PAQR3 inhibited breast cancer cell invasion and growth. Furthermore, PAQR3 expression was restored in MCF‑7 cells after treatment with the demethylating agent, 5-aza-2'-deoxycytidine, and the effect of demethylation induced invasion and proliferation suppression of MCF‑7 cells. Collectively, our results suggested that the aberrant methylation of PAQR3 underlies its downregulation in breast cancer and our data indicated that epigenetic silencing of PAQR3 gene expression by promoter hypermethylation may play an important role in breast cancer.

PAQR3 suppresses the proliferation, migration and tumorigenicity of human prostate cancer cells.

As a newly discovered tumor suppressor, the potential function of PAQR3 in human prostate cancer has not been demonstrated. In this study, we report that PAQR3 is able to inhibit the growth and migration of human prostate cancer cells both in vitro and in vivo. Overexpression of PAQR3 inhibits the proliferation of PC3 and DU145 cells by both MTT and colony formation assays. Consistently, knockdown of PAQR3 enhances the proliferation of these cells. In wound-healing and transwell assays, overexpression of PAQR3 reduces the migration of PC3 and DU145 cells, while PAQR3 knockdown increases it. In a tumor xenograft model, overexpression of PAQR3 suppresses tumor growth of PC3 cells in vivo, while PAQR3 knockdown promotes the tumor growth. PAQR3 is also able to inhibit serum-induced phosphorylation of AKT and ERK in both PC3 and DU145 cells. In addition, PAQR3 suppresses the expression of epithelial-mesenchymal transition (EMT) markers in PC3 cells. Collectively, these data indicate that PAQR3 has a tumor suppressive activity in human prostate cancer cells and may stand out as a potential therapeutic target for prostate cancers.

PAQR3 enhances Twist1 degradation to suppress epithelial-mesenchymal transition and metastasis of gastric cancer cells.

Twist1 is an essential transcription factor required to initiate epithelial-mesenchymal transition (EMT) and promote tumor metastasis. PAQR3 is a newly found tumor suppressor that is frequently downregulated in many types of human cancers. Downregulation of PAQR3 is associated with accelerated metastasis and poor prognosis of the patients with gastric cancers. In this study, we demonstrate that PAQR3 is actively involved in the degradation of Twist1 and whereby regulates EMT and metastasis of gastric cancer cells. PAQR3 overexpression reduces the protein level but not the mRNA level of Twist1. The protein stability and polyubiquitination of Twist1 are altered by PAQR3. PAQR3 forms a complex with Twist1 and BTRC, an E3 ubiquitin ligase. PAQR3 enhances the interaction between Twist1 and BTRC. Twist1 is mobilized from the nucleus to a proteasome-containing structure in the cytoplasm upon overexpression of PAQR3 and BTRC, which is required for PAQR3-induced degradation of Twist1. The Twist1 box domain of the Twist1 protein is required for the interaction of Twist1 with both PAQR3 and BTRC, indispensable for PAQR3-mediated degradation of Twist1. Both BTRC and Twist1 are required for the inhibitory effects of PAQR3 on migration and EMT phenotype of gastric cancers cells. Importantly, Twist1 is indispensable for the inhibitory effect of PAQR3 on metastasis of gastric cancer cells in vivo Collectively, these findings not only pinpoint that Twist1 mediates the modulatory function of PAQR3 on EMT and metastasis but also suggest that targeting Twist1 is a promising strategy to control metastasis of tumors with downregulation of PAQR3.

PAQR3 plays a suppressive role in laryngeal squamous cell carcinoma.

Laryngeal squamous cell carcinoma (LSCC) is a common type of head and neck malignancy worldwide. The molecular mechanism of LSCC remains not well understood. PAQR3 (progestin and AdipoQ receptors) is a member of the progestin and adipoQ receptor (PAQR) family. Many studies have showed that PAQR3 acts as a new tumor suppressor. However, its expression and functions in LSCC are still unknown. In our study, the expression of PAQR3 was downregulated in human LSCC tissues compared to that in adjacent tissues. Moreover, overexpression of PAQR3 suppressed LSCC cell proliferation and invasion. In addition, PAQR3 inhibited cell proliferation and invasion by regulating ERK phosphorylation. In conclusion, our data demonstrated that PAQR3 acted a tumor suppressive role in LSCC, providing a novel diagnostic and therapeutic option for LSCC in the future.

PAQR3 expression is downregulated in human breast cancers and correlated with HER2 expression.

PAQR3 is a newly discovered tumor suppressor and its functional role in breast cancer has not been well characterized. We report here that PAQR3 is associated with the progression and survival of human patients with breast cancer, as well as cell proliferation and migration of human breast cancer cells. PAQR3 mRNA level was robustly downregulated in human breast cancer samples compared with their corresponding para-cancerous histological normal tissues (n = 82, P < 0.0001). The mRNA level of PAQR3 was negatively correlated with HER2 expression (P < 0.0001) and disease-free survival of the patients (P < 0.0001). PAQR3 overexpression inhibited cell proliferation, colony formation and migration of breast cancer cells including MCF7, SKBR3, MDA-MD-231, MDA-MD-468 and MDA-MD-453 cells. Knockdown of PAQR3 in MDA-MD-231 cells elevated cell proliferation and migration. Inhibition of HER2 by trastuzumab increased PAQR3 expression in SKBR3 cells. In conclusion, PAQR3 expression is frequently downregulated in human breast cancers inversely correlated with HER2 expression. PAQR3 is able to modulate the proliferation and migration of breast cancer cells. Our data indicate that PAQR3 functions as a tumor suppressor in the development of human breast cancers.

The tumor suppressor role of PAQR3 in osteosarcoma.

Osteosarcoma is the most common primary bone malignancy; however, the molecular mechanisms of development are not well understood. Progestin and AdipoQ receptors (PAQR3), a protein specifically localized in the Golgi apparatus, was recently characterized as a new tumor suppressor. Little is known about the expression and function of PAQR3 in osteosarcoma. Here, we showed that PAQR3 was downregulated in osteosarcoma tissues compared with the adjacent normal regions in 80 paired samples. Moreover, lower levels of PAQR3 were associated with metastasis in clinical osteosarcoma patients. In addition, overexpression of PAQR3 in the osteosarcoma cell line MG-63 inhibited cell proliferation, migration, and invasion by promoting ERK phosphorylation. Taken together, our results indicated that PAQR3 might act as a tumor suppressor in osteosarcoma, providing a novel diagnostic and therapeutic option for human osteosarcoma in the future.

A Golgi-specific protein PAQR3 is closely associated with the progression, metastasis and prognosis of human gastric cancers.

The aim of this study is to determine whether PAQR3, a protein specifically localized in the Golgi apparatus, is associated with tumor progression, metastasis and survival of human patients with gastric cancer. PAQR3 expression status was investigated in a large panel of gastric cancer (n = 300) and their corresponding para-cancerous histological normal tissues (PCHNT) at both mRNA and protein levels. The correlation of PAQR3 expression levels with clinical features such as metastasis and prognosis was analyzed. The effect of PAQR3 on the growth and migration of gastric cancer cells was also determined. PAQR3 was frequently down-regulated in gastric cancer samples compared with PCHNT at both mRNA and protein levels (both P < 0.0001). The expression level of PAQR3 was negatively correlated with Helicobacter pylori infection (P < 0.0001), tumor size (P < 0.0001), tumor stage (P < 0.0001), venous and lymphatic invasion (P < 0.0001), distant and nodal metastasis (P < 0.0001), and patient survival (P < 0.0001). Down-regulation of PAQR3 was highly correlated with increased epithelial-mesenchymal transition (EMT) in gastric cancer samples. In addition, PAQR3 overexpression was able to negatively modulate cell proliferation, migration and EMT of gastric cancer cells. PAQR3 is markedly down-regulated in human gastric cancers. PAQR3 expression level is closely associated with the progression and metastasis of gastric cancers. PAQR3 is also a new genetic signature that can predict the prognosis of the patients with gastric cancer.

PAQR3 Has Modulatory Roles in Obesity, Energy Metabolism, and Leptin Signaling

Diet-induced obesity is commonly associated with leptin resistance, and attenuated leptin signaling contributes to the progression of obesity. PAQR3 is a member of the progesterone and AdipoQ receptor (PAQR) family with close homology to adiponectin receptors. We hypothesized that PAQR3 is implicated in the regulation of obesity and energy homeostasis. To address this hypothesis, we fed Paqr3-deleted mice with high-fat diet (HFD), followed by analyses to evaluate obesity, hepatic steatosis, insulin resistance, metabolic rate, and leptin signaling. We found that mice with deletion of Paqr3 are resistant to HFD-induced obesity and hepatic steatosis, accompanied by improvement of insulin resistance and insulin signaling. Paqr3-deleted mice have an increased energy expenditure and physical activity. HFD-induced leptin resistance is reversed by Paqr3 ablation. Overexpression of PAQR3 reduces leptin signaling whereas deletion of Paqr3 enhances leptin signaling in the hypothalamus. In conclusion, this study reveals that PAQR3 has an important physiological function in modulating obesity, energy metabolism, and leptin signaling.

PAQR3 Modulates Insulin Signaling by Shunting Phosphoinositide 3-Kinase p110α to the Golgi Apparatus

Phosphoinositide 3-kinase (PI3K) mediates insulin actions by relaying signals from insulin receptors (IRs) to downstream targets. The p110α catalytic subunit of class IA PI3K is the primary insulin-responsive PI3K implicated in insulin signaling. We demonstrate here a new mode of spatial regulation for the p110α subunit of PI3K by PAQR3 that is exclusively localized in the Golgi apparatus. PAQR3 interacts with p110α, and the intracellular targeting of p110α to the Golgi apparatus is reduced by PAQR3 downregulation and increased by PAQR3 overexpression. Insulin-stimulated PI3K activity and phosphoinositide (3,4,5)-triphosphate production are enhanced by Paqr3 deletion and reduced by PAQR3 overexpression in hepatocytes. Deletion of Paqr3 enhances insulin-stimulated phosphorylation of AKT and glycogen synthase kinase 3β, but not phosphorylation of IR and IR substrate-1 (IRS-1), in hepatocytes, mouse liver, and skeletal muscle. Insulin-stimulated GLUT4 translocation to the plasma membrane and glucose uptake are enhanced by Paqr3 ablation. Furthermore, PAQR3 interacts with the domain of p110α involved in its binding with p85, the regulatory subunit of PI3K. Overexpression of PAQR3 dose-dependently reduces the interaction of p85α with p110α. Thus, PAQR3 negatively regulates insulin signaling by shunting cytosolic p110α to the Golgi apparatus while competing with p85 subunit in forming a PI3K complex with p110α.

PAQR3 Plays a Suppressive Role in the Tumorigenesis of Colorectal Cancers

PAQR3 is a member of the progestin and adipoQ receptor (PAQR) family and was recently characterized as a spatial regulator that negatively modulates Ras/Raf/MEK/ERK signaling cascade. However, little is known about the physiological functions of PAQR3 in the tumorigenesis of colorectal cancers. The function of PAQR3 in colorectal cancer development in mice was analyzed by crossing Paqr3-depleted mice with Apc(Min/+) mice that have a germline mutation of the gene-encoding tumor suppressor adenomatous polyposis coli (APC). The survival time and tumor area in the small intestine of the Apc(Min/+) mice was significantly aggravated by Paqr3 deletion. The cell proliferation rate, anchorage-independent growth, EGF-stimulated ERK phosphorylation and EGF-induced nuclear accumulation of β-catenin were inhibited by PAQR3 overexpression and enhanced by PAQR3 knockdown in SW-480 colorectal cancer cells. In humans, the expression level of PAQR3 was significantly decreased in colorectal cancer samples in comparison with adjacent normal tissues. In addition, the expression level of PAQR3 was inversely associated with tumor grade in the colorectal cancer samples. Collectively, our data reveal for the first time that PAQR3 has a tumor suppressor activity in the development of colorectal cancers.