Beneficial Effects of PIN1 Inhibition on Diabetes Mellitus: A Concise Review

Type 2 diabetes mellitus is a long-term medical illness in which the body either becomes resistant to insulin or fails to produce it sufficiently. Mostly, combinatorial therapy is required to control blood glucose levels. However, combinatorial therapy has detrimental side effects. The prevalence of the cases and subsequent increases in medical costs of the same intimidate human health globally. While there have been a lot of studies focused on developing diabetic regimens that work to lower blood glucose levels, their effectiveness is short-lived because of unfavorable side effects, such as weight gain and hypoglycemia. In recent years, the PIN1 (protein interacting with NIMA) enzyme has attracted the attention of researchers. Previous studies suggested that PIN1 may act on the various substrates that are involved in the progression of T2DM and also help in the management of diabetes-related disorders. Thus, the focus of the current review is to examine the correlation between PIN1, T2DM and its related disorders and explore the possibility of developing novel therapeutic targets through PIN1 inhibition.

PIN1 promotes the metastasis of cholangiocarcinoma cells by RACK1-mediated phosphorylation of ANXA2

BACKGROUND

Cholangiocarcinoma (CCA), a primary hepatobiliary malignancy, is characterized by a poor prognosis and a lack of effective treatments. Therefore, the need to explore novel therapeutic approaches is urgent. While the role of Peptidylprolyl Cis/Trans Isomerase, NIMA-Interacting 1 (PIN1) has been extensively studied in various tumor types, its involvement in CCA remains poorly understood.

METHODS

In this study, we employed tissue microarray (TMA), reverse transcription-polymerase chain reaction (RT-PCR), and The Cancer Genome Atlas (TCGA) database to assess the expression of PIN1. Through in vitro and in vivo functional experiments, we investigated the impact of PIN1 on the adhesion and metastasis of CCA. Additionally, we explored downstream molecular pathways using RNA-seq, western blotting, co-immunoprecipitation, immunofluorescence, and mass spectrometry techniques.

RESULTS

Our findings revealed a negative correlation between PIN1 overexpression and prognosis in CCA tissues. Furthermore, high PIN1 expression promoted CCA cell proliferation and migration. Mechanistically, PIN1 functioned as an oncogene by regulating ANXA2 phosphorylation, thereby promoting CCA adhesion. Notably, the interaction between PIN1 and ANXA2 was facilitated by RACK1. Importantly, pharmacological inhibition of PIN1 using the FDA-approved drug all-trans retinoic acid (ATRA) effectively suppressed the metastatic potential of CCA cells in a nude mouse lung metastasis model.

CONCLUSION

Overall, our study emphasizes the critical role of the PIN1/RACK1/ANXA2 complex in CCA growth and functionality, highlighting the potential of targeting PIN1 as a promising therapeutic strategy for CCA.

PIN1P1 is activated by CREB1 and promotes gastric cancer progression via interacting with YBX1 and upregulating PIN1

Long noncoding RNAs (lncRNAs) play critical roles in the carcinogenesis and progression of cancers. However, the role and mechanism of the pseudogene lncRNA PIN1P1 in gastric carcinoma remain unclear. The expression and effects of lncRNA PIN1P1 in gastric cancer were investigated. The transcriptional regulation of CREB1 on PIN1P1 was determined by ChIP and luciferase assays. The mechanistic model of PIN1P1 in gastric cancer was further explored by RNA pull-down, RIP and western blot analysis. PIN1P1 was overexpressed in gastric cancer tissues, and upregulated PIN1P1 predicted poor prognosis in patients. CREB1 was directly combined with the promoter region of PIN1P1 to promote the transcription of PIN1P1. CREB1-mediated enhanced proliferation, migration and invasion could be partially reversed by downregulation of PIN1P1. Overexpressed PIN1P1 promoted the proliferation, migration and invasion of gastric cancer cells, whereas decreased PIN1P1 showed the opposite effects. PIN1P1 directly interacted with YBX1 and promoted YBX1 protein expression, leading to upregulation of PIN1, in which E2F1 may be involved. Silencing of YBX1 during PIN1P1 overexpression could partially rescue PIN1 upregulation. PIN1, the parental gene of PIN1P1, was elevated in gastric cancer tissues, and its upregulation was correlated with poor patient outcomes. PIN1 facilitated gastric cancer cell proliferation, migration and invasion. To sum up, CREB1-activated PIN1P1 could promote gastric cancer progression through YBX1 and upregulating PIN1, suggesting that it is a potential target for gastric cancer.

Substrate recognition and transport mechanism of the PIN-FORMED auxin exporters

Auxins are pivotal plant hormones that regulate plant growth and transmembrane polar auxin transport (PAT) direct patterns of development. The PIN-FORMED (PIN) family of membrane transporters mediate auxin export from the plant cell and play crucial roles in PAT. Here we describe the recently solved structures of PIN transporters, PIN1, PIN3, and PIN8, and also their mechanisms of substrate recognition and transport of auxin. We compare structures of PINs in both inward- and outward-facing conformations, as well as PINs with different binding configurations for auxin. By this comparative analysis, a model emerges for an elevator transport mechanism. Central structural elements necessary for function are identified, and we show that these are shared with other distantly related protein families.

Restoration of miR-328a-5p function curtails hypoxic pulmonary hypertension through a mechanism involving PIN1/GSK3β/β-catenin axis

Recent evidence has highlighted the involvement of microRNAs (miRs) in hypoxic pulmonary hypertension (PH), which can be induced under hypoxic conditions. We intend to explore whether the miR-328a-5p/PIN1 axis affects hypoxic PH by regulating the GSK3β/β-catenin signaling pathway. The GEO database was retrieved to single out key miRs affecting hypoxic PH. It was observed that downregulation of miR-328a-5p occurred in hypoxia-induced PH samples. The binding affinity between miR-328a-5p to PIN1 was predicted by a bioinformatics tool and verified using a dual luciferase reporter gene assay. Rat primary pulmonary artery smooth muscle cells (PASMCs) were exposed to hypoxia for in vitro cell experiments. miR-328a-5p could target and downregulate PIN1 expression, leading to suppressed GSK3β/β-catenin activation. In addition, GSK3β/β-catenin inactivation curtailed hypoxia-induced vascular inflammatory responses and proliferation and migration in PASMCs in vitro. A hypoxic PH model was established in SD rats to observe the effects of miR-328a-5p on hemodynamic parameters and right heart remodeling. It was demonstrated in vivo that miR-328a-5p downregulated PIN1 expression to suppress GSK3β/β-catenin signaling, thereby reducing the vascular inflammatory response and alleviating disease progression in hypoxia-induced PH rats. The evidence provided by our study highlighted the involvement of miR-328a-5p in the translational suppression of PIN1 and the blockade of the GSK3β/β-catenin signaling pathway, resulting in attenuation of hypoxic PH progression.

Reduced PIN1 gene expression in neocortical and limbic brain regions in female Alzheimer's patients correlates with cognitive and neuropathological phenotypes

Women have a higher incidence of Alzheimer's disease (AD), even after adjusting for increased longevity. Thus, there is an urgent need to identify the molecular networks that underpin the sex-associated risk of AD. Recent efforts have identified PIN1 as a key regulator of tau phosphorylation signaling pathway. Pin1 is the only gene, to date, that when deleted can cause both tau and Aβ-related pathologies in an age-dependent manner. We analyzed multiple brain transcriptomic datasets focusing on sex differences in PIN1 mRNA levels, in an aging and AD cohort, which revealed reduced PIN1 levels driven by females. Then, we validated this observation in an independent dataset (ROS/MAP) which also revealed that PIN1 is negatively correlated with multiregional neurofibrillary tangle density and global cognitive function, in females only. Additional analysis revealed a decrease in PIN1 in subjects with mild cognitive impairment (MCI) compared with aged individuals, again, driven predominantly by female subjects. Our results show that while both male and female AD patients show decreased PIN1 expression, changes occur before the onset of clinical symptoms of AD in females and correlate to early events associated with AD risk (e.g., synaptic dysfunction). These changes are specific to neurons, and may be a potential prognostic marker to assess AD risk in the aging population and even more so in AD females with increased risk of AD.

ERF1 inhibits lateral root emergence by promoting local auxin accumulation and repressing ARF7 expression

Lateral roots (LRs) are crucial for plants to sense environmental signals in addition to water and nutrient absorption. Auxin is key for LR formation, but the underlying mechanisms are not fully understood. Here, we report that Arabidopsis ERF1 inhibits LR emergence by promoting local auxin accumulation with altered distribution and regulating auxin signaling. Loss of ERF1 increases LR density compared with the wild type, whereas ERF1 overexpression causes the opposite phenotype. ERF1 enhances auxin transport by upregulating PIN1 and AUX1, resulting in excessive auxin accumulation in the endodermal, cortical, and epidermal cells surrounding LR primordia. Furthermore, ERF1 represses ARF7 transcription, thereby downregulating the expression of cell-wall remodeling genes that facilitate LR emergence. Together, our study reveals that ERF1 integrates environmental signals to promote local auxin accumulation with altered distribution and repress ARF7, consequently inhibiting LR emergence in adaptation to fluctuating environments.

Non-POU Domain-Containing Octomer-Binding (NONO) protein expression and stability promotes the tumorigenicity and activation of Akt/MAPK/β-catenin pathways in human breast cancer cells

Breast cancer is one of the most common cancers with a high mortality rate, underscoring the need to identify new therapeutic targets. Here we report that non-POU domain-containing octamer-binding (NONO) protein is overexpressed in breast cancer and validated the interaction of the WW domain of PIN1 with c-terminal threonine-proline (thr-pro) motifs of NONO. The interaction of NONO with PIN1 increases the stability of NONO by inhibiting its proteasomal degradation, and this identifies PIN1 as a positive regulator of NONO in promoting breast tumor development. Functionally, silencing of NONO inhibits the growth, survival, migration, invasion, epithelial to mesenchymal transition (EMT), and stemness of breast cancer cells in vitro. A human metastatic breast cancer cell xenograft was established in transparent zebrafish (Danio rerio) embryos to study the metastatic inability of NONO-silenced breast cancer cells in vivo. Mechanistically, NONO depletion promotes the expression of the PDL1 cell-surface protein in breast cancer cells. The identification of novel interactions of NONO with c-Jun and β-catenin proteins and activation of the Akt/MAPK/β-catenin signaling suggests that NONO is a novel regulator of Akt/MAPK/β-catenin signaling pathways. Taken together, our results indicated an essential role of NONO in the tumorigenicity of breast cancer and could be a potential target for anti-cancerous drugs. Video Abstract.

Loss-of-function of gynoecium-expressed phospholipase pPLAIIγ triggers maternal haploid induction in Arabidopsis

Production of in planta haploid embryos that inherit chromosomes from only one parent can greatly increase breeding efficiency via quickly generating homozygous plants, called doubled haploid. One of the main players of in planta haploid induction is a pollen-specific phospholipase A, which is able, when mutated, to induce in vivo haploid induction in numerous monocots. However, no functional orthologous gene has been identified in dicots plants. Here, we show that loss-of-function of gynoecium-expressed phospholipase AII (pPLAIIγ) triggers maternal haploid plants in Arabidopsis, at an average rate of 1.07%. Reciprocal crosses demonstrate that haploid plants are triggered from the female side and not from the pollen, and the haploid plants carry the maternal genome. Promoter activity of pPLAIIγ shows enriched expression in the funiculus of flower development stages 13 and 18, and pPLAIIγ fused to yellow fluorescent protein reveals a plasma-membrane localization Interestingly, the polar localized PIN1 at the basal plasma membrane of the funiculus was all internalized in pplaIIγ mutants, suggesting that altered PIN1 localization in female organ could play a role in maternal haploid induction.

Hydrogen sulfide alleviates osmotic stress-induced root growth inhibition by promoting auxin homeostasis

Hydrogen sulfide (H₂ S) promotes plant tolerance against various environmental cues, and d-cysteine desulfhydrase (DCD) is an enzymatic source of H₂ S to enhance abiotic stress resistance. However, the role of DCD-mediated H₂ S production in root growth under abiotic stress remains to be further elucidated. Here, we report that DCD-mediated H₂ S production alleviates osmotic stress-mediated root growth inhibition by promoting auxin homeostasis. Osmotic stress up-regulated DCD gene transcript and DCD protein levels and thus H₂ S production in roots. When subjected to osmotic stress, a dcd mutant showed more severe root growth inhibition, whereas the transgenic lines DCDox overexpressing DCD exhibited less sensitivity to osmotic stress in terms of longer root compared to the wild-type. Moreover, osmotic stress inhibited root growth through repressing auxin signaling, whereas H₂ S treatment significantly alleviated osmotic stress-mediated inhibition of auxin. Under osmotic stress, auxin accumulation was increased in DCDox but decreased in dcd mutant. H₂ S promoted auxin biosynthesis gene expression and auxin efflux carrier PIN-FORMED 1 (PIN1) protein level under osmotic stress. Taken together, our results reveal that mannitol-induced DCD and H₂ S in roots promote auxin homeostasis, contributing to alleviating the inhibition of root growth under osmotic stress.

Key role of PIN1 in telomere maintenance and oncogenic behavior in a human glioblastoma model

PIN1 is the only known enzyme capable of recognizing and isomerizing the phosphorylated Serine/Threonine‑Proline motif. Through this mechanism, PIN1 controls diverse cellular functions, including telomere maintenance. Both PIN1 overexpression and its involvement in oncogenic pathways are involved in several cancer types, including glioblastoma (GBM), a lethal disease with poor therapeutic resources. However, knowledge of the role of PIN1 in GBM is limited. Thus, the present work aimed to study the role of PIN1 as a telomere/telomerase regulator and its contribution to tumor biology. PIN1 knockout (KO) LN‑229 cell variant using CRISPR/Cas9 was developed and compared with PIN1 LN‑229 expressing cells. To study the effect of PIN1 absence, status of NF‑κB pathway was evaluated by luciferase reporter gene assay and quantitative PCR. Results revealed that PIN1 deletion in GBM cells diminished the active levels of NF‑κB and decrease the transcription of il‑8 and htert genes. Then, telomere/telomerase related processes were studied by RQ‑TRAP assay and telomere length determination by qPCR, obtaining a reduction both in telomerase activity as in telomere length in PIN1 KO cells. In addition, measurement of SA β‑galactosidase and caspase‑3 activities revealed that loss of PIN1 triggers senescence and apoptosis. Finally, migration, cell cycle progression and tumorigenicity were studied by flow cytometry/western blot, Transwell assay and in vivo experiments, respectively. PIN1 deletion decreased migration as well as cell cycle progression by increasing doubling time and also resulted in the loss of LN‑229 cell ability to form tumors in mice. These results highlight the role of PIN1 in telomere homeostasis and GBM progression, which supports PIN1 as a potential molecular target for the development of novel therapeutic agents for GBM treatment.

pin2 mutant agravitropic root phenotype is conditional and nutrient-sensitive

Plants have the capacity to sense and adapt to environmental factors using the phytohormone auxin as a major regulator of tropism and development. Among these responses, gravitropism is essential for plant roots to grow downward in the search for nutrients and water. We discovered a new mutant allele of the auxin efflux transporter PIN2 that revealed that pin2 agravitropic root mutants are conditional and nutrient-sensitive. We describe that nutrient composition of the medium, rather than osmolarity, can revert the agravitropic root phenotype of pin2. Indeed, on phosphorus- and nitrogen-deprived media, the agravitropic root defect was restored independently of primary root growth levels. Slow and fast auxin responses were evaluated using DR5 and R2D2 probes, respectively, and revealed a strong modulation by nutrient composition of the culture medium. We evaluated the role of PIN and AUX auxin transporters and demonstrated that neither PIN3 nor AUX1 are involved in this process. However, we observed the ectopic expression of PIN1 in the epidermis in the pin2 mutant background associated with permissive, but not restrictive, conditions. This ectopic expression was associated with a restoration of the asymmetric accumulation of auxin necessary for the reorientation of the root according to gravity. These observations suggest a strong regulation of auxin distribution by nutrients availability, directly impacting root's ability to drive their gravitropic response.

Cinobufacini injection suppresses the proliferation of human osteosarcoma cells by inhibiting PIN1-YAP/TAZ signaling pathway

Cinobufacini injection (CI), an aqueous extract of Cutis Bufonis, is clinically used for cancer therapy in China, but its molecular mechanism for the treatment of osteosarcoma (OS) remains unclear. We constructed U2OS ectopic subcutaneous tumor model to verify the anti-OS effect of CI in vivo. Meanwhile, cell proliferation of U2OS and MG63 cells was monitored in vitro using the CCK-8 assay, colony formation and morphological changes. Cell cycle arrest and apoptosis were detected by flow cytometry and western blot, which showed that CI significantly inhibited proliferation, induced cell cycle arrest and apoptosis in human OS cells. The further RNA-seq results identified that the Hippo signaling pathway was involved in the anti-OS effect of CI. YAP/TAZ are two major components of the Hippo pathway in breast cancer and are positively regulated by prolyl isomerase PIN1, we assessed their role in OS using both clinicopathological sections and western blots. CI also inhibited PIN1 enzyme activity in a dose-dependent manner, which resulted in impaired PIN1, YAP, and TAZ expression in vitro and in vivo. Additionally, 15 potential compounds of CI were found to occupy the PIN1 kinase domain and inhibit its activity. In summary, CI plays an anti-OS role by down-regulating the PIN1-YAP/TAZ pathway.

The metabolic crosstalk between PIN1 and the tumour microenvironment

Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1) is a member of a family of peptidyl-prolyl isomerases that specifically recognizes and binds phosphoproteins, catalyzing the rapid cis-trans isomerization of phosphorylated serine/threonine-proline motifs, which leads to changes in the structures and activities of the targeted proteins. Through this complex mechanism, PIN1 regulates many hallmarks of cancer including cell autonomous metabolism and the crosstalk with the cellular microenvironment. Many studies showed that PIN1 is largely overexpressed in cancer turning on a set of oncogenes and abrogating the function of tumor suppressor genes. Among these targets, recent evidence demonstrated that PIN1 is involved in lipid and glucose metabolism and accordingly, in the Warburg effect, a characteristic of tumor cells. As an orchestra master, PIN1 finely tunes the signaling pathways allowing cancer cells to adapt and take advantage from a poorly organized tumor microenvironment. In this review, we highlight the trilogy among PIN1, the tumor microenvironment and the metabolic program rewiring.

Mechanical Regulation of Redox Balance via the Induction of the PIN1/NRF2/ARE Axis in Pancreatic Cancer

Pancreatic cancer is one of the most lethal malignancies. Desmoplastic stroma and metabolic reprogramming are two hallmarks of pancreatic cancer that support its malignant biological behaviors. However, the underlying mechanism by which the stroma maintain the redox balance remains unclear in pancreatic ductal adenocarcinoma (PDAC). Here, we demonstrated that the physical properties of the stroma could regulate the expression of PIN1 in pancreatic cancer cells. Moreover, we found that hard matrix-cultured pancreatic cancer cells induced the upregulation of PIN1 expression. Since PIN1 maintained redox balance via synergistic activation of NRF2 transcription, PIN1 promoted the expression of NRF2 to induce the expression of intracellular antioxidant response element (ARE)-driven genes. Consequently, the antioxidant stress ability of PDAC was increased, and the intracellular level of reactive oxygen species (ROS) was decreased. Thus, PIN1 is expected to be an important target for the treatment of PDAC, especially PDAC with an exuberant desmoplastic stroma.

The ROP2 GTPase Participates in Nitric Oxide (NO)-Induced Root Shortening in Arabidopsis

Nitric oxide (NO) is a versatile signal molecule that mediates environmental and hormonal signals orchestrating plant development. NO may act via reversible S-nitrosation of proteins during which an NO moiety is added to a cysteine thiol to form an S-nitrosothiol. In plants, several proteins implicated in hormonal signaling have been reported to undergo S-nitrosation. Here, we report that the Arabidopsis ROP2 GTPase is a further potential target of NO-mediated regulation. The ROP2 GTPase was found to be required for the root shortening effect of NO. NO inhibits primary root growth by altering the abundance and distribution of the PIN1 auxin efflux carrier protein and lowering the accumulation of auxin in the root meristem. In rop2-1 insertion mutants, however, wild-type-like root size of the NO-treated roots were maintained in agreement with wild-type-like PIN1 abundance in the meristem. The ROP2 GTPase was shown to be S-nitrosated in vitro, suggesting that NO might directly regulate the GTPase. The potential mechanisms of NO-mediated ROP2 GTPase regulation and ROP2-mediated NO signaling in the primary root meristem are discussed.

SUE4, a novel PIN1-interacting membrane protein, regulates acropetal auxin transport in response to sulfur deficiency

Sulfur (S) is an essential macronutrient for plants and a signaling molecule in abiotic stress responses. It is known that S availability modulates root system architecture; however, the underlying molecular mechanisms are largely unknown. We previously reported an Arabidopsis gain-of-function mutant sulfate utilization efficiency4 (sue4) that could tolerate S deficiency during germination and early seedling growth with faster primary root elongation. Here, we report that SUE4, a novel plasma membrane-localized protein, interacts with the polar auxin transporter PIN1, resulting in reduced PIN1 protein levels and thus decreasing auxin transport to the root tips, which promotes primary root elongation. Moreover, SUE4 is induced by sulfate deficiency, consistent with its role in root elongation. Further analyses showed that the SUE4-PIN1 interaction decreased PIN1 levels, possibly through 26 S proteasome-mediated degradation. Taken together, our finding of SUE4-mediated root elongation is consistent with root adaptation to highly mobile sulfate in soil, thus revealing a novel component in the adaptive response of roots to S deficiency.

Histone Acetyltransferase GCN5 Affects Auxin Transport during Root Growth by Modulating Histone Acetylation and Gene Expression of PINs

General Control Non-Derepressible 5 (GCN5) is a histone acetyltransferase that targets multiple genes and is essential for the acetylation of Lysine residues in the N-terminal tail of histone H3 in Arabidopsis. GCN5 interacts with the transcriptional coactivator Alteration/Deficiency in Activation 2b (ADA2b), which enhances its activity functioning in multiprotein complexes, such as the Spt-Ada-Gcn5-Acetyltransferase complex (SAGA). Mutations in GCN5 and ADA2b result in pleiotropic phenotypes, including alterations in the growth of roots. Auxin is known to regulate root development by modulating gene expression patterns. Auxin moves polarly during plant growth via the Pin-formed (PIN) auxin efflux transport proteins. The effect of GCN5 and ADA2b on auxin distribution at different stages of early root growth (4 to 7 days post-germination) was studied using the reporter lines DR5rev::GFP and PIN1::PIN1-GFP. In wild-type plants, auxin efflux transporter PIN1 expression increases from the fourth to the seventh day of root growth. The PIN1 expression was reduced in the roots of gcn5-1 and ada2b-1 compared to the wild type. The expression of PIN1 in ada2b-1 mutants is confined only to the meristematic zone, specifically in the stele cells, whereas it is almost abolished in the elongation zone. Gene expression analysis showed that genes associated with auxin transport, PIN1, PIN3 and PIN4, are downregulated in gcn5-1 and ada2b-1 mutants relative to the wild type. As a result, auxin accumulation was also reduced in gcn5-1 and ada2b-1 compared to wild-type roots. Furthermore, acetylation of Lysine 14 of histone H3 (H3K14) was also affected in the promoter and coding region of PIN1, PIN3 and PIN4 genes during root growth of Arabidopsis in gcn5 mutants. In conclusion, GCN5 acts as a positive regulator of auxin distribution in early root growth by modulating histone H3 acetylation and the expression of auxin efflux transport genes.

Mitochondrial GPAT-derived LPA controls auxin-dependent embryonic and postembryonic development

Membrane properties are emerging as important cues for the spatiotemporal regulation of hormone signaling. Lysophosphatidic acid (LPA) evokes multiple biological responses by activating G protein-coupled receptors in mammals. In this study, we demonstrated that LPA derived from the mitochondrial glycerol-3-phosphate acyltransferases GPAT1 and GPAT2 is a critical lipid-based cue for auxin-controlled embryogenesis and plant growth in Arabidopsis thaliana. LPA levels decreased, and the polarity of the auxin efflux carrier PIN-FORMED1 (PIN1) at the plasma membrane (PM) was defective in the gpat1 gpat2 mutant. As a consequence of distribution defects, instructive auxin gradients and embryonic and postembryonic development are severely compromised. Further cellular and genetic analyses revealed that LPA binds directly to PIN1, facilitating the vesicular trafficking of PIN1 and polar auxin transport. Our data support a model in which LPA provides a lipid landmark that specifies membrane identity and cell polarity, revealing an unrecognized aspect of phospholipid patterns connecting hormone signaling with development.

PIN1 protects auditory hair cells from senescence via autophagy

Background

Age-related hearing loss is an increasing sensorineural hearing loss. But the pathogenesis of ARHL has not been clarified. Herein, we studied the role and significance of PIN1 in regulating autophagy activity in senescence HEI-OC1cells and HCs.

Methods and Results

C57BL/6 mice and HEI-OC1 cells were contained in our research. Transfection of plasmids and juglone were used to upregulate or inhibit the PIN 1 expression. Immunofluorescence and Western blot were used to detect the expression of PIN1, LC3, p62, p21 and p16 protein levels in the hair cells of C57BL/6 mice cochleae and HEI-OC1 cells. Senescence-associated β-galactosidase (SA-β-gal) staining was used to investigate the senescent level.The results of this study showed that the level of autophagy increased in the senescent auditory hair cells. When inhibited the autophagy level with 3-MA, the senescent HEI-OC1 cells were alleviated. The autophagy activity in senescent HEI-OC1 cells also could be reduced by overexpressing PIN1 protein. On the contrary, inhibiting PIN1 could increase the autophagy level of senescent cells and cochlear hair cells.

Conclusion

PIN1 might regulate autophagy activity to induce the senescent of HEI-OC1cells and HCs, which will provide a theoretical support for the prevention and treatment of age-related hearing loss.

Inhibition of the PIN1-NRF2/GPX4 axis imparts sensitivity to cisplatin in cervical cancer cells

The incidence of cervical cancer (CC) ranks the fourth in female malignant tumors globally. Chemoresistance is one of the main causes of treatment failure in advanced recurrent CC. Prolyl isomerase 1 (PIN1) is overexpressed in a variety of tumors, and is closely associated with the malignant potential of tumor cells, such as transformation, proliferation, invasion and metastasis. In the present study, we demonstrate that cell death induced by suppression of PIN1 could be inhibited by ferrostatin-1 (Fer-1) and ferroptosis biomarkers including lactate dehydrogenase (LDH) release, lipid peroxidation and malondialdehyde (MDA) are upregulated by downregulating PIN1. We then discover that abrogation of PIN1 greatly decreases the level of glutathione peroxidase 4 (GPX4) and the level of PIN1 is positively correlated with the level of GPX4. Furthermore, the knockdown of PIN1 promotes ferroptosis induced by RSL3. The mechanism involves PIN1 silencing which downregulates GPX4 by decreasing the level of nuclear factor E2-related factor 2 (NRF2). Furthermore, overexpression of NRF2 inhibits RSL3-mediated ferroptosis of CC cells when PIN1 is silenced. In addition, our results indicate that cisplatin (DDP) induces ferroptosis, which is restrained by overexpression of PIN1. The PIN1 inhibitor, KPT-6566, promotes the cytotoxic effect of DDP. The present study reveals that PIN1 affects ferroptosis and sensitivity to DDP in CC cells via the NRF2/GPX4 axis, thereby identifying PIN1 as a potential therapeutic target for CC.

PIN1-mediated ROS production is involved in antagonism of N-acetyl-L-cysteine against arsenic-induced hepatotoxicity

Arsenic, a widely existing environmental contaminant, is recognized to be toxic to multiple organs. Exposure to arsenic results in liver damage via excessive production of reactive oxidative species (ROS). PIN1 regulates the levels of ROS. N-acetyl-L-cysteine (NAC) is an ROS scavenger that protects the hepatic functions. Whether PIN1 plays a regulatory role in NAC-mediated antagonism against arsenic hepatotoxicity remains largely unknown. In our study, the protective effects of NAC against arsenic (NaAsO2)-induced hepatotoxicity were evaluated in vitro and in vivo. Arsenic exposure induced cytotoxicity by increasing the intracellular ROS production, impairing mitochondrial function and inducing apoptosis in L02 hepatocytes. Overexpression of PIN1 markedly protected against arsenic cytotoxicity, decreased ROS levels, and mitigated mitochondrial dysfunction and apoptosis in L02 cells. However, loss of PIN1 further aggravated arsenic-induced cytotoxicity and abolished the protective effects of NAC in L02 cells. An in vivo study showed that pretreatment with NAC rescued arsenic-induced liver injury by restoring liver function and suppressing hepatic oxidative stress. Overexpression of PIN1 in mice transfected with AAV-Pin1 relieved arsenic-induced liver dysfunction and hepatic oxidative stress. Taken together, our study identified PIN1 as a novel intervention target for antagonizing arsenic-induced hepatotoxicity, highlighting a new pharmacological mechanism of NAC targeting PIN1 in antagonism against arsenic toxicity.

The Hydrophilic Loop of Arabidopsis PIN1 Auxin Efflux Carrier Harbors Hallmarks of an Intrinsically Disordered Protein

Much of plant development depends on cell-to-cell redistribution of the plant hormone auxin, which is facilitated by the plasma membrane (PM) localized PIN FORMED (PIN) proteins. Auxin export activity, developmental roles, subcellular trafficking, and polarity of PINs have been well studied, but their structure remains elusive besides a rough outline that they contain two groups of 5 alpha-helices connected by a large hydrophilic loop (HL). Here, we focus on the PIN1 HL as we could produce it in sufficient quantities for biochemical investigations to provide insights into its secondary structure. Circular dichroism (CD) studies revealed its nature as an intrinsically disordered protein (IDP), manifested by the increase of structure content upon thermal melting. Consistent with IDPs serving as interaction platforms, PIN1 loops homodimerize. PIN1 HL cytoplasmic overexpression in Arabidopsis disrupts early endocytic trafficking of PIN1 and PIN2 and causes defects in the cotyledon vasculature formation. In summary, we demonstrate that PIN1 HL has an intrinsically disordered nature, which must be considered to gain further structural insights. Some secondary structures may form transiently during pairing with known and yet-to-be-discovered interactors.

Association of polymorphisms in PIN1 with progression and susceptibility in gastric cancer

Background: High expression of PIN1 is associated with gastric cancer progression and risk. Patients & methods: Two single-nucleotide polymorphisms in PIN1, rs2233678 and rs2233679, were examined in gastric cancer patients using PCR-restriction fragment length polymorphism. Results: The rs2233678 GC genotype and C alleles correlated with a decreased susceptibility to gastric cancer. The stratification analysis indicated that the rs2233678 GC genotype was inversely related to gastric cancer risk in never smokers, never drinkers and patients with stage I/II disease. Males and ever drinkers carrying the rs2233679 CT genotype had a mildly elevated susceptibility to gastric cancer. Conclusion: The PIN1 single-nucelotide polymorphisms rs2233678 and rs2233679 correlate with the risk of gastric cancer.

Integrated Bioinformatics Analyses of PIN1, CKX, and Yield-Related Genes Reveals the Molecular Mechanisms for the Difference of Seed Number Per Pod Between Soybean and Cowpea

There is limited advancement on seed number per pod (SNPP) in soybean breeding, resulting in low yield in China. To address this issue, we identified PIN1 and CKX gene families that regulate SNPP in Arabidopsis, analyzed the differences of auxin and cytokinin pathways, and constructed interaction networks on PIN1, CKX, and yield-related genes in soybean and cowpea. First, the relative expression level (REL) of PIN1 and the plasma membrane localization and phosphorylation levels of PIN1 protein were less in soybean than in cowpea, which make auxin transport efficiency lower in soybean, and its two interacted proteins might be involved in serine hydrolysis, so soybean has lower SNPP than cowpea. Then, the CKX gene family, along with its positive regulatory factor ROCK1, had higher REL and less miRNA regulation in soybean flowers than in cowpea ones. These lead to higher cytokinin degradation level, which further reduces the REL of PIN1 and decreases soybean SNPP. We found that VuACX4 had much higher REL than GmACX4, although the two genes essential in embryo development interact with the CKX gene family. Next, a tandem duplication experienced by legumes led to the differentiation of CKX3 into CKX3a and CKX3b, in which CKX3a is a key gene affecting ovule number. Finally, in the yield-related gene networks, three cowpea CBP genes had higher RELs than two soybean CBP genes, low RELs of three soybean-specific IPT genes might lead to a decrease in cytokinin synthesis, and some negative and positive SNPP regulation were found, respectively, in soybean and cowpea. These networks may explain the SNPP difference in the two crops. We deduced that ckx3a or ckx3a ckx6 ckx7 mutants, interfering CYP88A, and over-expressed DELLA increase SNPP in soybean. This study reveals the molecular mechanism for the SNPP difference in the two crops, and provides an important idea for increasing soybean yield.

Local regulation of auxin transport in root-apex transition zone mediates aluminium-induced Arabidopsis root-growth inhibition

Aluminium (Al) stress is a major limiting factor for worldwide crop production in acid soils. In Arabidopsis thaliana, the TAA1-dependent local auxin biosynthesis in the root-apex transition zone (TZ), the major perception site for Al toxicity, is crucial for the Al-induced root-growth inhibition, while the mechanism underlying Al-regulated auxin accumulation in the TZ is not fully understood. In the present study, the role of auxin transport in Al-induced local auxin accumulation in the TZ and root-growth inhibition was investigated. Our results showed that PIN-FORMED (PIN) proteins such as PIN1, PIN3, PIN4 and PIN7 and AUX1/LAX proteins such as AUX1, LAX1 and LAX2 were all ectopically up-regulated in the root-apex TZ in response to Al stress and coordinately regulated local auxin accumulation in the TZ and root-growth inhibition. The ectopic up-regulation of PIN1 in the TZ under Al stress was regulated by both ethylene and auxin, with auxin signalling acting downstream of ethylene. Al-induced PIN1 up-regulation and auxin accumulation in the root-apex TZ was also regulated by the calossin-like protein BIG. Together, our results provide insight into how Al stress induces local auxin accumulation in the TZ and root-growth inhibition through the local regulation of auxin transport.

The prolyl-isomerase PIN1 is essential for nuclear Lamin-B structure and function and protects heterochromatin under mechanical stress

Chromatin organization plays a crucial role in tissue homeostasis. Heterochromatin relaxation and consequent unscheduled mobilization of transposable elements (TEs) are emerging as key contributors of aging and aging-related pathologies, including Alzheimer's disease (AD) and cancer. However, the mechanisms governing heterochromatin maintenance or its relaxation in pathological conditions remain poorly understood. Here we show that PIN1, the only phosphorylation-specific cis/trans prolyl isomerase, whose loss is associated with premature aging and AD, is essential to preserve heterochromatin. We demonstrate that this PIN1 function is conserved from Drosophila to humans and prevents TE mobilization-dependent neurodegeneration and cognitive defects. Mechanistically, PIN1 maintains nuclear type-B Lamin structure and anchoring function for heterochromatin protein 1α (HP1α). This mechanism prevents nuclear envelope alterations and heterochromatin relaxation under mechanical stress, which is a key contributor to aging-related pathologies.

HSP90 affects root growth in Arabidopsis by regulating the polar distribution of PIN1

Auxin homeostasis and signaling affect a broad range of developmental processes in plants. The interplay between HSP90 and auxin signaling is channeled through the chaperoning capacity of the HSP90 on the TIR1 auxin receptor. The sophisticated buffering capacity of the HSP90 system through the interaction with diverse signaling protein components drastically shapes genetic circuitries regulating various developmental aspects. However, the elegant networking capacity of HSP90 in the global regulation of auxin response and homeostasis has not been appreciated. Arabidopsis hsp90 mutants were screened for gravity response. Phenotypic analysis of root meristems and cotyledon veins was performed. PIN1 localization in hsp90 mutants was determined. Our results showed that HSP90 affected the asymmetrical distribution of PIN1 in plasma membranes and influenced its expression in prompt cell niches. Depletion of HSP90 distorted polar distribution of auxin, as the acropetal auxin transport was highly affected, leading to impaired root gravitropism and lateral root formation. The essential role of the HSP90 in auxin homeostasis was profoundly evident from early development, as HSP90 depletion affected embryo development and the pattern formation of veins in cotyledons. Our data suggest that the HSP90-mediated distribution of PIN1 modulates auxin distribution and thereby auxin signaling to properly promote plant development.

Mixed Lineage Kinase 3 phosphorylates prolyl-isomerase PIN1 and potentiates GLI1 signaling in pancreatic cancer development

The transcription factor Glioma-Associated Oncogene Homolog 1 (GLI1) is activated by sonic hedgehog (SHH) cascade and is an established driver of pancreatic ductal adenocarcinoma (PDAC). However, therapies targeting upstream hedgehog signaling have shown little to no efficacy in clinical trials. Here, we identify Mixed Lineage Kinase 3 (MLK3) as a druggable regulator of oncogenic GLI1. Earlier, we reported that MLK3 phosphorylated a peptidyl-prolyl isomerase PIN1 on the S138 site, and the PIN1-pS138 translocated to the nucleus. In this report, we identify GLI1 as one of the targets of PIN1-pS138 and demonstrate that PIN1-pS138 is upregulated in human PDAC and strongly associates with the upregulation of GLI1 and MLK3 expression. Moreover, we also identified two new phosphorylation sites on GLI1, T394, and S1089, which are directly phosphorylated by MLK3 to promote GLI1 nuclear translocation, transcriptional activity, and cell proliferation. Additionally, pharmacological inhibition of MLK3 by CEP-1347 promoted apoptosis in PDAC cell lines, reduced tumor burden, extended survival, and reduced GLI1 expression in the Pdx1-Cre x LSL-KRASG12D x LSL-TP53R172H (KPC) mouse model of PDAC. These findings collectively suggest that MLK3 is an important regulator of oncogenic GLI1 and that therapies targeting MLK3 warrant consideration in the management of PDAC patients.

The Rab Geranylgeranyl Transferase Beta Subunit Is Essential for Embryo and Seed Development in Arabidopsis thaliana

Auxin is a key regulator of plant development affecting the formation and maturation of reproductive structures. The apoplastic route of auxin transport engages influx and efflux facilitators from the PIN, AUX and ABCB families. The polar localization of these proteins and constant recycling from the plasma membrane to endosomes is dependent on Rab-mediated vesicular traffic. Rab proteins are anchored to membranes via posttranslational addition of two geranylgeranyl moieties by the Rab Geranylgeranyl Transferase enzyme (RGT), which consists of RGTA, RGTB and REP subunits. Here, we present data showing that seed development in the rgtb1 mutant, with decreased vesicular transport capacity, is disturbed. Both pre- and post-fertilization events are affected, leading to a decrease in seed yield. Pollen tube recognition at the stigma and its guidance to the micropyle is compromised and the seed coat forms incorrectly. Excess auxin in the sporophytic tissues of the ovule in the rgtb1 plants leads to an increased tendency of autonomous endosperm formation in unfertilized ovules and influences embryo development in a maternal sporophytic manner. The results show the importance of vesicular traffic for sexual reproduction in flowering plants, and highlight RGTB1 as a key component of sporophytic-filial signaling.

Arabidopsis vascular complexity and connectivity controls PIN-FORMED1 dynamics and lateral vein patterning during embryogenesis

Arabidopsis VASCULATURE COMPLEXITY AND CONNECTIVITY (VCC) is a plant-specific transmembrane protein that controls the development of veins in cotyledons. Here, we show that the expression and localization of the auxin efflux carrier PIN-FORMED1 (PIN1) is altered in vcc developing cotyledons and that overexpression of PIN1-GFP partially rescues vascular defects of vcc in a dosage-dependent manner. Genetic analyses suggest that VCC and PINOID (PID), a kinase that regulates PIN1 polarity, are both required for PIN1-mediated control of vasculature development. VCC expression is upregulated by auxin, likely as part of a positive feedback loop for the progression of vascular development. VCC and PIN1 localized to the plasma membrane in pre-procambial cells but were actively redirected to vacuoles in procambial cells for degradation. In the vcc mutant, PIN1 failed to properly polarize in pre-procambial cells during the formation of basal strands, and instead, it was prematurely degraded in vacuoles. VCC plays a role in the localization and stability of PIN1, which is crucial for the transition of pre-procambial cells into procambial cells that are involved in the formation of basal lateral strands in embryonic cotyledons.

Impact of PIN1 Inhibition on Tumor Progression and Chemotherapy Sensitivity in Colorectal Cancer

BACKGROUND

Deregulated PIN1 is associated with cancer development and progression. Herein, for the first time, we evaluate the roles that PIN1 in tumorigenic characteristics of colorectal cancer (CRC) cells.

METHODS

In this study, PIN1 expression was knocked down in SW-48 cells by synthetic small interfering RNA (siRNA). After confirming the knockdown of PIN1, cell viability, colony formation, apoptosis, autophagy, cancer stem cell (CSC)-related genes, CSC-related signaling pathways, cell migration, and 5-FU chemosensitivity were evaluated in vitro.

RESULTS

Transfection of PIN1 siRNA into SW-48 cells inhibited cancer cell proliferation, migration, and increased apoptosis and autophagy. Transfected SW-48 cells had lower properties of CSCs through the inhibition of β-catenin and Notch1 gene expression. Moreover, inhibition of PIN1 enhanced the inhibitory effect of 5-FU on SW-48 cell proliferation.

CONCLUSION

Our results indicated that targeting of PIN1 serves as a promising therapeutic solution for the suppression of tumor progression processes in CRC.

Rab-dependent vesicular traffic affects female gametophyte development in Arabidopsis

Eukaryotic cells rely on the accuracy and efficiency of vesicular traffic. In plants, disturbances in vesicular trafficking are well studied in quickly dividing root meristem cells or polar growing root hairs and pollen tubes. The development of the female gametophyte, a unique haploid reproductive structure located in the ovule, has received far less attention in studies of vesicular transport. Key molecules providing the specificity of vesicle formation and its subsequent recognition and fusion with the acceptor membrane are Rab proteins. Rabs are anchored to membranes by covalently linked geranylgeranyl group(s) that are added by the Rab geranylgeranyl transferase (RGT) enzyme. Here we show that Arabidopsis plants carrying mutations in the gene encoding the β-subunit of RGT (rgtb1) exhibit severely disrupted female gametogenesis and this effect is of sporophytic origin. Mutations in rgtb1 lead to internalization of the PIN1 and PIN3 proteins from the basal membranes to vesicles in provascular cells of the funiculus. Decreased transport of auxin out of the ovule is accompanied by auxin accumulation in tissue surrounding the growing gametophyte. In addition, female gametophyte development arrests at the uni- or binuclear stage in a significant portion of the rgtb1 ovules. These observations suggest that communication between the sporophyte and the developing female gametophyte relies on Rab-dependent vesicular traffic of the PIN1 and PIN3 transporters and auxin efflux out of the ovule.

A preliminary identification of PIN1 SNP linkage in patients with coronary heart disease from Handan, China

Our aim was to perform an initial assessment of the polymorphic patterns of the PIN1 gene in patients with coronary heart disease (CHD). The PIN1-encoded protein (Pin1) suppresses eNOS-NO signaling and may impair cardiovascular function. Blood collection, DNA extraction, PCR amplification and gene sequencing were performed for thirty CHD participants living in central China, focusing on nine single nucleotide polymorphisms (SNPs). Their genetic linkages were revealed and their allele frequencies were compared with SNP data from the NCBI. Three major linkage patterns were identified: [1.rs2287839-5.rs2233682], [3.rs2233679-4.rs1077220-8.rs2287838] and [6.rs889162-7.rs2010457], suggesting correlated involvement in CHD and possible simultaneous genetic origin in ancient times. The frequencies of six SNPs are consistent with the NCBI data, while the frequencies of three SNPs (2.rs2233678, 4.rs1077220 and 9.rs4804461) are not consistent with the NCBI. Especially, the 3.rs2233679-4.rs1077220 linkage is different from other populations worldwide and may be an interesting genetic characteristic of Chinese CHD patients. Predictably, 1.rs2287839, 2.rs2233678, 3.rs2233679 and 5.rs2233682 may be strongly associated with CHD risk, although this requires future verification. The PIN1 SNP linkages lay a new genetic foundation for discovering novel molecular mechanisms of CHD and for exploring PIN1-based targeted treatment of CHD with nitric oxide regulatory therapies in clinical practice.

DNA methylation analysis of candidate genes associated with dementia in peripheral blood

Aim: To investigate whether genes implicated in dementia pathogenesis are differently methylated in peripheral blood. Materials & methods: Participants included 160 cognitively healthy individuals aged 70+ years: 73 who were subsequently diagnosed with dementia and 87 controls matched on age, gender, education, smoking and baseline cognition. A total of 49 participants also provided blood samples at diagnosis. Blood DNA methylation of APOE, APP, BDNF, PIN1, SNCA and TOMM40 was examined. Results: A total of 56 of 299 probes were differentially methylated in dementia compared with controls and 39 probes prior to diagnosis. The greatest effect size was in APP (cg19423170, Δ-8.32%, adjusted p = 0.009 at diagnosis; cg19933173, Δ-4.18%, adjusted p < 0.0001 prediagnosis). Conclusion: Genes implicated in dementia pathogenesis show differential blood methylation in dementia, even prior to diagnosis.

Melatonin regulates Aβ production/clearance balance and Aβ neurotoxicity: A potential therapeutic molecule for Alzheimer's disease

Alzheimer's disease (AD) is an age-related neurodegenerative disease with multiple predisposing factors and complicated pathogenesis. Aβ peptide is one of the most important pathogenic factors in the etiology of AD. Accumulating evidence indicates that the imbalance of Aβ production and Aβ clearance in the brain of AD patients leads to Aβ deposition and neurotoxic Aβ oligomer formation. Melatonin shows a potent neuroprotective effect and can prevent or slow down the progression of AD, supporting the view that melatonin is a potential therapeutic molecule for AD. Melatonin modulates the regulatory network of secretase expression and affects the function of secretase, thereby inhibiting amyloidogenic APP processing and Aβ production. Additionally, melatonin ameliorates Aβ-induced neurotoxicity and probably promotes Aβ clearance through glymphatic-lymphatic drainage, BBB transportation and degradation pathways. In this review, we summarize and discuss the role of melatonin against Aβ-dependent AD pathogenesis. We explore the potential cellular and molecular mechanisms of melatonin on Aβ production and assembly, Aβ clearance, Aβ neurotoxicity and circadian cycle disruption. We summarize multiple clinical trials of melatonin treatment in AD patients, showing that melatonin has a promising effect on improving sleep quality and cognitive function. This review aims to stimulate further research on melatonin as a potential therapeutic agent for AD.

Long Noncoding RNA FBXL19-AS1 Expedites Cell Growth, Migration and Invasion in Cervical Cancer by miR-193a-5p/PIN1 Signaling

Background

Cervical cancer is one of the most prevalent malignancies in gynecology with increasing incidence in recent years. Long noncoding RNAs (lncRNAs) have been reported to regulate human cancers including cervical cancer. F-box and leucine-rich repeat protein 19 antisense RNA 1 (FBXL19-AS1) have been unmasked to exert carcinogenic functions in several cancers except cervical cancer.

Aim

Present study hammered at investigating the function and mechanism of FBXL19-AS1 in cervical cancer.

Methods

RT-qPCR was utilized to test gene expression. EdU staining, colony formation, transwell, flow cytometry and TUNEL assays were applied for measuring the impact of FBXL19-AS1 on cervical cancer cell functions. Moreover, RIP, RNA pull-down and luciferase reporter assays were utilized for detecting the correlations among FBXL19-AS1, miR-193a-5p and PIN1 (peptidylprolyl cis/trans isomerase, NIMA-interacting 1).

Results

FBXL19-AS1 exhibited elevated expression in cervical cancer tissues and cells. Silencing FBXL19-AS1 repressed cell proliferation through arresting cell cycle and stimulating apoptosis, and losing FBXL19-AS1 also restrained cell migration and invasion. Also, we discovered FBXL19-AS1 as a miR-193a-5p sponge, while miR-193a-5p was a tumor inhibitor in cervical cancer. Further, PIN1 was proved as the miR-193a-5p target, and FBXL19-AS1 augmented PIN1 expression in cervical cancer via sequestering miR-193a-5p. Of note, PIN1 accelerated the progression of cervical cancer, and its upregulation counteracted the impacts of depleted FBXL19-AS1 on cervical cancer cell functions.

Conclusion

FBXL19-AS1 contributes to malignant phenotypes in cervical cancer by sponging miR-193a-5p and regulating PIN1.

The peptidyl prolyl isomerase, PIN1 induces angiogenesis through direct interaction with HIF-2α

PIN1, the peptidyl-prolyl isomerase (PPIase), is an enzyme that changes the conformation of phosphoproteins. The conformational change induced by PIN1 alters the function and stability of the target proteins. PIN1 is overexpressed in many different types of malignancies, including breast, lung, cervical, brain and colorectal tumors. PIN1 overexpression has been associated with activation of multiple oncogenic signaling pathways during tumor development. Hypoxia-inducible factor 2α (HIF-2α), a transcription factor activated in hypoxia, plays a role in erythropoiesis, glycolysis, tissue invasion, metastasis and angiogenesis. In this study, we found the direct interaction between HIF-2α and PIN1 in colorectal cancer HCT116 cells. Notably, serine 16 and lysine 63 residues of PIN1 were critical for its interaction with HIF-2α. When PIN1 protein was silenced by transient transfection of PIN1 short interfering RNA, the expression of HIF-2α was attenuated under a hypoxic condition. Moreover, genetic and pharmacologic inhibition of PIN1 abrogated the expression of vascular endothelial growth factor and angiogenesis. The cycloheximide chase experiment revealed the stabilization of HIF-2α by PIN1. Both WW and PPIase domains of PIN1 appear to be critical for its interaction with HIF-2α.

The association of rs2233679 in the PIN1 gene promoter with the risk of Coronary Artery Disease in Chinese female individuals

BACKGROUNDS

Vascular atherosclerosis leads to various cardiovascular and cerebrovascular diseases. Nitric oxide (NO) promotes vasodilatation and prevents Coronary Artery Disease (CAD). Pin1 suppresses NO production by down-regulating the activity of endothelial nitric oxide synthase (eNOS). Whether the genetic polymorphisms of the PIN1 gene (encoding Pin1) are implicated in CAD deserves investigations in human beings.

METHODS

A total of 210 CAD patients and control individuals (all females) were enrolled, and their genotypes of rs2233679 (-667C/T, a key SNP in the promoter of PIN1 gene) were sequenced. T-test, chi-square test, odds ratio (OR) and 95% confidence interval (95% CI) were calculated to evaluate Hardy-Weinberg equilibrium, varied genetic distribution and relative CAD risk.

RESULTS

The differences in age, BMI, triglyceride, total cholesterol, low-density and high density cholesterol between the CAD and control groups were not significant (all P>0.05), and Hardy-Weinberg equilibrium was observed in the two groups (both P>0.05). The frequency of -667T allele in the CAD group was higher than that in the control group. The genotype -667TT elicited a higher hazardous risk of CAD compared to the genotype -667CC (OR=1.85, 95% CI: 0.75-4.53) as well as the genotypes CC+CT (OR=1.97, 95% CI: 0.86-4.49).

CONCLUSIONS

We firstly show that the allele -667T in the PIN1 promoter may elicit a higher CAD-risk than -667C, and the -667TT genotype of PIN1 may be a new genetic biomarker for increased incidence of CAD. These novel observations put forward a new understanding of the PIN1-CAD genetic relationship in humans, potentially contributing to both cardiovascular and cerebrovascular disorders.

Mini Review: Opposing Pathologies in Cancer and Alzheimer's Disease: Does the PI3K/Akt Pathway Provide Clues?

This minireview is a brief overview examining the roles of insulin-like growth factors (IGFs) and the PI3K/Akt pathway in two apparently unconnected diseases: Alzheimer's dementia and cancer. For both, increased age is a major risk factor, and, in accord with the global rise in average life expectancy, their prevalence is also increasing. Cancer, however, involves excessive cell proliferation and metastasis, whereas Alzheimer's disease (AD) involves cell death and tissue destruction. The apparent "inverse" nature of these disease states is examined here, but also some important commonalities in terms of the PI3K/Akt pathway, glucose utilization and cell deregulation/death. The focus here is on four key molecules associated with this pathway; notably, the insulin receptor substrate 1 (IRS-1), cellular tumor antigen p53 (p53), peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1) and low-density lipoprotein receptor-related protein-1 (LRP1), all previously identified as potential therapeutic targets for both diseases. The insulin-resistant state, commonly reported in AD brain, results in neuronal glucose deprivation, due to a dampening down of the PI3K/Akt pathway, including overactivity of the mammalian target of rapamycin 1 (mTORC1) complex, hyperphosphorylation of p53 and neuronal death. This contrasts with cancer, where there is overstimulation of the PI3K/Akt pathway and the suppression of mTORC1 and p53, enabling abundant energy and unrestrained cell proliferation. Although these disease states appear to be diametrically opposed, the same key molecules are controlling pathology and, with differential targeting of therapeutics, may yet provide a beneficial outcome for both.

Auxin canalization and vascular tissue formation by TIR1/AFB-mediated auxin signaling in Arabidopsis

Plant survival depends on vascular tissues, which originate in a self-organizing manner as strands of cells co-directionally transporting the plant hormone auxin. The latter phenomenon (also known as auxin canalization) is classically hypothesized to be regulated by auxin itself via the effect of this hormone on the polarity of its own intercellular transport. Correlative observations supported this concept, but molecular insights remain limited. In the current study, we established an experimental system based on the model Arabidopsis thaliana, which exhibits auxin transport channels and formation of vasculature strands in response to local auxin application. Our methodology permits the genetic analysis of auxin canalization under controllable experimental conditions. By utilizing this opportunity, we confirmed the dependence of auxin canalization on a PIN-dependent auxin transport and nuclear, TIR1/AFB-mediated auxin signaling. We also show that leaf venation and auxin-mediated PIN repolarization in the root require TIR1/AFB signaling. Further studies based on this experimental system are likely to yield better understanding of the mechanisms underlying auxin transport polarization in other developmental contexts.

Pin1 promotes pancreatic cancer progression and metastasis by activation of NF-κB-IL-18 feedback loop

Objectives

Accumulated evidence suggests that Pin1 contributes to oncogenesis of diverse cancers. However, the underlying mechanism of oncogenic function of Pin1 in PDAC requires further exploration.

Materials and Methods

IHC was performed using PDAC tissues. Western blot, PCR, immunofluorescence and transwell were performed using cell lines. GSEA were applied for possible downstream pathways. ChIP assay and dual luciferase were used for assessment of transcriptional activity.

Results

Both Pin1 and IL‐18 levels are increased in primary PDAC tissues and that their levels are positively correlated. High expression of IL‐18 is a predictor of poor prognoses. Pin1 promoted pancreatic cancer cell proliferation and motility by increasing IL‐18 expression, while Pin1 knockdown also inhibited the tumour‐promoting effect of IL‐18. Both Pin1 and IL‐18 could enhance the NFκB activity in pancreatic cancer cells. When bound to the p65 protein, Pin1 promoted p65 phosphorylation and its nuclear translocation. In the nucleus, Pin1 and p65 simultaneously bound to the IL‐18 promoter and enhanced IL‐18 transcription. In addition, recruitment of p65 to the IL‐18 promoter was decreased in Pin1‐silenced cells.

Conclusions

Our study improves the understanding of Pin1 in tumour‐promoting inflammation in PDAC, which is a hallmark of cancer; Pin1 interacted with p65 in PDAC and enhanced NF‐κB signalling and downstream transcriptional activation of IL‐18, with increased IL‐18 continuously activating NF‐κB signalling, which then forms a positive feedback loop.

Clathrin-mediated trafficking and PIN trafficking are required for auxin canalization and vascular tissue formation in Arabidopsis

The flexible development of plants is characterized by a high capacity for post-embryonic organ formation and tissue regeneration, processes, which require tightly regulated intercellular communication and coordinated tissue (re-)polarization. The phytohormone auxin, the main driver for these processes, is able to establish polarized auxin transport channels, which are characterized by the expression and polar, subcellular localization of the PIN1 auxin transport proteins. These channels are demarcating the position of future vascular strands necessary for organ formation and tissue regeneration. Major progress has been made in the last years to understand how PINs can change their polarity in different contexts and thus guide auxin flow through the plant. However, it still remains elusive how auxin mediates the establishment of auxin conducting channels and the formation of vascular tissue and which cellular processes are involved. By the means of sophisticated regeneration experiments combined with local auxin applications in Arabidopsis thaliana inflorescence stems we show that (i) PIN subcellular dynamics, (ii) PIN internalization by clathrin-mediated trafficking and (iii) an intact actin cytoskeleton required for post-endocytic trafficking are indispensable for auxin channel formation, de novo vascular formation and vascular regeneration after wounding. These observations provide novel insights into cellular mechanism of coordinated tissue polarization during auxin canalization.

A coherent feed-forward loop drives vascular regeneration in damaged aerial organs of plants growing in a normal developmental context

Aerial organs of plants, being highly prone to local injuries, require tissue restoration to ensure their survival. However, knowledge of the underlying mechanism is sparse. In this study, we mimicked natural injuries in growing leaves and stems to study the reunion between mechanically disconnected tissues. We show that PLETHORA (PLT) and AINTEGUMENTA (ANT) genes, which encode stem cell-promoting factors, are activated and contribute to vascular regeneration in response to these injuries. PLT proteins bind to and activate the CUC2 promoter. PLT proteins and CUC2 regulate the transcription of the local auxin biosynthesis gene YUC4 in a coherent feed-forward loop, and this process is necessary to drive vascular regeneration. In the absence of this PLT-mediated regeneration response, leaf ground tissue cells can neither acquire the early vascular identity marker ATHB8, nor properly polarise auxin transporters to specify new venation paths. The PLT-CUC2 module is required for vascular regeneration, but is dispensable for midvein formation in leaves. We reveal the mechanisms of vascular regeneration in plants and distinguish between the wound-repair ability of the tissue and its formation during normal development.

major during chemical and thermal denaturation

PIN1 proteins are a class of peptidyl prolyl cis-trans isomerases (PPIases), which have been implicated in numerous cellular functions like cell cycle progression, transcriptional control, signal transduction, promotion of oncogenesis and host-parasite interactions. In this work, the unfolding mechanism of a single domain PIN1 from Leishmania major (LmPIN1) has been characterized during thermal and denaturant-induced unfolding by differential scanning calorimetry (DSC), fluorescence and circular dichroism. Further, MD simulations have been performed to structurally probe the possible stages of its unfolding process. Both the fluorescence and CD data confirm classical two-state unfolding transitions for urea and GdnHCl. The thermal unfolding of LmPIN1, characterized by DSC, could optimally be fitted to a non two-state transition curve exhibiting two T_m's (53 °C and 57 °C) suggesting the possibility of an intermediate. Thermal unfolding of the modeled LmPIN1 by MD simulation shows that the unfolding process is initiated by increased fluctuations (dynamics) spanning residues 70-80, followed by perturbations in the sheet system and disjuncture of helix-sheet packing. Importantly, simulation and fluorescence quenching studies clearly suggest the possibility of the presence of residual structures of LmPIN1 even after complete denaturation.

Function of PIN1 in Cancer Development and Its Inhibitors as Cancer Therapeutics

Peptidyl-prolyl isomerase (PIN1) specifically binds and isomerizes the phosphorylated serine/threonine-proline (pSer/Thr-Pro) motif, which results in the alteration of protein structure, function, and stability. The altered structure and function of these phosphorylated proteins regulated by PIN1 are closely related to cancer development. PIN1 is highly expressed in human cancers and promotes cancer as well as cancer stem cells by breaking the balance of oncogenes and tumor suppressors. In this review, we discuss the roles of PIN1 in cancer and PIN1-targeted small-molecule compounds.

Targeting PIN1 as a Therapeutic Approach for Hepatocellular Carcinoma

PIN1 is a peptidyl-prolyl cis/trans isomerase that specifically binds and catalyzes the cis/trans isomerization of the phosphorylated serine or threonine residue preceding a proline (pSer/Thr-Pro) motif of its interacting proteins. Through this phosphorylation-dependent prolyl isomerization, PIN1 is involved in the regulation of various important cellular processes including cell cycle progression, cell proliferation, apoptosis and microRNAs biogenesis; hence its dysregulation contributes to malignant transformation. PIN1 is highly expressed in hepatocellular carcinoma (HCC). By fine-tuning the functions of its interacting proteins such as cyclin D1, x-protein of hepatitis B virus and exportin 5, PIN1 plays an important role in hepatocarcinogenesis. Growing evidence supports that targeting PIN1 is a potential therapeutic approach for HCC by inhibiting cell proliferation, inducing cellular apoptosis, and restoring microRNAs biogenesis. Novel formulation of PIN1 inhibitors that increases in vivo bioavailability of PIN1 inhibitors represents a promising future direction for the therapeutic strategy of HCC treatment. In this review, the mechanisms underlying PIN1 over-expression in HCC are explored. Furthermore, we also discuss the roles of PIN1 in HCC tumorigenesis and metastasis through its interaction with various phosphoproteins. Finally, recent progress in the therapeutic options targeting PIN1 for HCC treatment is examined and summarized.

All-trans Retinoic Acid Overcomes Acquired Resistance to PLX4032 via Inhibition of PIN1 in Melanoma Cells

BACKGROUND/AIM

PLX4032 is commonly used in the treatment of advanced melanoma patients with BRAF-V600E mutation. The aim of this study was to elucidate the mechanisms by which up-regulation of PIN1 confers PLX4032 resistance in melanoma.

MATERIALS AND METHODS

The expression of PIN1 as well as the cytotoxic effects of combinatorial treatment of PLX4032 and all-trans retinoic acid (ATRA) were investigated by immunoblotting, MTT assay, TUNEL assay, and soft agar assay.

RESULTS

PIN1 expression is up-regulated in A375R cells, a PLX4032-resistant subline of melanoma cells generated from an A375 cell line, compared to parental A375 cells. Indeed, PIN1 positively regulated the expression of EGFR in A375R cells and led to activation of the RAF/MEK/ERK pathway. Importantly, PLX4032, when used in combination with ATRA, an inhibitor of PIN1, reduced EGFR expression, and consequently reduced cell viability and anchorage-independent growth of A375R cells compared to PLX4032 alone. Furthermore, co-treatment with ATRA and PLX4032 increased cleaved PARP and DNA fragmentation in A375R cells.

CONCLUSION

PIN1 plays an important role in the development of PLX4032 resistance through up-regulation of EGFR expression.

BRCA1-BARD1: the importance of being in shape

The breast cancer type-1 susceptibility protein (BRCA1) contributes to genome integrity through homologous recombinational DNA repair and by protecting stalled replication forks from nucleolytic degradation. We recently discovered that fork protection requires a conformational change of BRCA1 unimportant to homologous recombination repair, indicating separate roles for BRCA1 in these pathways.