Proline-rich Acidic Protein 1 Research Articles

Intestinal SURF4 is essential for apolipoprotein transport and lipoprotein secretion

ObjectiveLipoprotein assembly and secretion in the small intestine are critical for dietary fat absorption. Surfeit locus protein 4 (SURF4) serves as a cargo receptor, facilitating the cellular transport of multiple proteins and mediating hepatic lipid secretion in vivo. However, its involvement in intestinal lipid secretion is not fully understood. In this study, we investigated the role of SURF4 in intestinal lipid absorption. MethodsWe generated intestine-specific Surf4 knockout mice and characterized the phenotypes. Additionally, we investigated the underlying mechanisms of SURF4 in intestinal lipid secretion using proteomics and cellular models. ResultsWe unveiled that SURF4 is indispensable for apolipoprotein transport and lipoprotein secretion. Intestine-specific Surf4 knockout mice exhibited ectopic lipid deposition in the small intestine and hypolipidemia. Deletion of SURF4 impeded the transport of apolipoprotein A1 (ApoA1), proline-rich acidic protein 1 (PRAP1), and apolipoprotein B48 (ApoB48) and hindered the assembly and secretion of chylomicrons and high-density lipoproteins. ConclusionsSURF4 emerges as a pivotal regulator of intestinal lipid absorption via mediating the secretion of ApoA1, PRAP1 and ApoB48.

Impact of Amplified Oncogenes on Salivary Gland Carcinomas.

In normal epithelia, proto-oncogenes regulate critical intra- or intercellular functions, including cell growth and proliferation, apoptosis, and signaling transduction from the cell periphery (extracellular space) to the nucleus mediated by different pathways. Oncogenes are the mutated or amplified forms of the corresponding proto-oncogenes that are crucially involved in cell neoplastic and malignant transformation during carcinogenesis. Salivary gland carcinomas (SGCs) demonstrate a variety of histogenetic types. They are characterized by a broad spectrum of chromosomal and gene alterations. In particular, amplifications in specific genes [human epidermal growth factor receptor 2 (HER2), human epidermal growth factor receptor 4 (HER4), epidermal growth factor receptor (EGFR), anaplastic lymphoma kinase (ALK), Mouse double minute 2 homolog (MDM2), androgen receptor (AR), programmed death (ligand 1 (PD-L1), neurogenic differentiation factor 2 (NEUROD2), phosphatidylinositol 3,4,5-trisphosphate-dependent RAC exchanger 1 protein (PREX1), cyclin-dependent kinase4/6 (CDK4/6), proline-rich acidic protein 1 (PRAP1), kell antigen system (KEL), glutamate receptor subunit epsilon 2 (GRIN2D), Ewing sarcoma RNA-binding protein 1 (EWSR1), MYC proto-oncogene (MYC)] combined or not with chromosomal numerical imbalances (aneuploidy/ polysomy/monosomy) form different genetic signatures affecting the response to monoclonal antibody-based, oncologicaly targeted regimens. Different SGC histotypes demonstrate specific combinations of mutated/amplified genes that modify their clinicohistological features. In the current molecular review, we present the most important amplified oncogenes and their impact on the biological behavior of SGCS.

The mechanism of influence of kaempferol on proline-rich acidic protein 1 (PRAP1) expression after percutaneous coronary intervention (PCI) was investigated based on sini decoction and siwu decoction

The mechanism of influence of kaempferol on proline-rich acidic protein 1 (PRAP1) expression after percutaneous coronary intervention (PCI) was investigated based on sini decoction and siwu decoction

Proline-rich acidic protein 1 upregulates mitotic arrest deficient 1 to promote cisplatin-resistance of colorectal carcinoma by restraining mitotic checkpoint complex assembly.

Background: The mechanism underlying cisplatin resistance in colorectal carcinoma (CRC) has not yet been elucidated. This study is aimed to illustrate the indispensable role of proline-rich acidic protein 1 (PRAP1) in cisplatin-resistant CRC. Methods: Cell viability and apoptosis were monitored using cell counting kit-8 and flow cytometry. Immunofluorescence and morphological analysis were used to determine mitotic arrest in cells. In vivo drug resistance was evaluated using a tumor xenograft assay. Results: PRAP1 was highly expressed in cisplatin-resistant CRC. PRAP1-upregulation in HCT-116 cells increased chemoresistance to cisplatin, whereas RNAi-mediated knockdown of PRAP1 sensitized cisplatin-resistant HCT-116 cells (HCT-116/DDP) to cisplatin. PRAP1-upregulation in HCT-116 cells hindered mitotic arrest and the formation of mitotic checkpoint complexes (MCC), followed by an increase in multidrug-resistant proteins such as p-glycoprotein 1 and multidrug resistance-associated protein 1, while PRAP1-knockdown in HCT-116/DDP cells partly restored colcemid-induced mitotic arrest and MCC assembly, resulting in decreased multidrug-resistant protein levels. PRAP1 downregulation-mediated sensitization to cisplatin in HCT-116/DDP cells was abolished by the inhibition of mitotic kinase activity by limiting MCC assembly. Additionally, PRAP1-upregulation increased cisplatin-resistance in CRC in vivo. Mechanistically, PRAP1 increased the expression of mitotic arrest deficient 1 (MAD1), that competitively binds to mitotic arrest deficient 2 (MAD2) in cisplatin-resistant CRC cells, leading to failed assembly of MCC and subsequent chemotherapy resistance. Conclusion: PRAP1-overexpression caused cisplatin resistance in CRC. Possibly, PRAP1 induced an increase in MAD1, which competitively interacted with MAD2 and subsequently restrained the formation of MCC, resulting in CRC cells escape from the supervision of MCC and chemotherapy resistance.

Characterization of PRAP1 During Murine Gestation

The development of Assisted Reproductive Technologies, such as in vitro fertilization (IVF), has allowed many couples struggling with fertility to conceive. However, IVF has a 60% failure rate. The leading cause of IVF failure is understood to be unsuccessful implantation. Improper or defective implantation leads to improper placentation which can affect fetal growth and development. While it is known that implantation is a complex reproductive process dependent on both competent embryos and a receptive uterus, many aspects of implantation remain unclear. Proline Rich Acidic Protein 1 (PRAP1), a 17 kDa protein, is expressed and secreted by the uterine endometrium. In the absence of PRAP1, female mice show defective implantation suggesting that PRAP1 has a role in this process. Nonetheless, PRAP1 remains largely uncharacterized. The objectives of this study are to characterize the role of PRAP1 during gestation and implantation. We hypothesize PRAP1 plays a role in implantation/placentation and overall pregnancy maintenance. Using timed pregnancies of wildtype C47BL/6J mice, uterine tissue was collected for each day of gestation and four days post‐partum, then analyzed by RT‐qPCR, immunofluorescence with a‐PRAP1 antibodies, and H&E staining. We found that Prap1 transcript is highly expressed during gestation compared to non‐ovulating females. Additionally, PRAP1 is downregulated during the window of implantation beginning at day 3.5 and increases on day 5.5. This increase continues and peaks just prior to parturition, and PRAP1 expression decreases 1000x within 4 days post‐partum. Immunofluorescence analysis demonstrated PRAP1 is localized to the endometrial epithelia during early gestation, but localized specifically to the anti‐mesometrial epithelia that interfaces with the amnion during mid‐ and late‐gestation. We have also found that our PRAP1−/− female mice have a slightly reduced fecundability (the ability to achieve a live birth from one cycle’s exposure to the risk of pregnancy) attributable to a reduced rate of implantation. We conclude PRAP1 plays a role in implantation/placentation and overall pregnancy maintenance.

Proline-Rich Acidic Protein 1 (PRAP1) Protects the Gastrointestinal Epithelium From Irradiation-Induced Apoptosis.

Background & AimsThe intestinal epithelium must be resilient to physiochemical stress to uphold the physiological barrier separating the systemic compartment from the microbial and antigenic components of the gut lumen. Identifying proteins that mediate protection and enhancing their expression is therefore a clear approach to promote intestinal health. We previously reported that oral ingestion of the probiotic Lactobacillus rhamnosus GG not only induced the expression of several recognized cytoprotective factors in the murine colon, but also many genes with no previously described function, including the gene encoding proline-rich acidic protein 1 (PRAP1). PRAP1 is a highly expressed protein in the epithelium of the gastrointestinal tract and we sought to define its function in this tissue.MethodsPurified preparations of recombinant PRAP1 were analyzed biochemically and PRAP1 antisera were used to visualize localization in tissues. Prap1-/- mice were characterized at baseline and challenged with total body irradiation, then enteroids were generated to recapitulate the irradiation challenge ex vivo.ResultsPRAP1 is a 17-kilodalton intrinsically disordered protein with no recognizable sequence homology. PRAP1 expression levels were high in the epithelia of the small intestine. Although Prap1-/- mice presented only mild phenotypes at baseline, they were highly susceptible to intestinal injury upon challenge. After irradiation, the Prap1-/- mice showed accelerated death with a significant increase in apoptosis and p21 expression in the small intestinal epithelium.ConclusionsPRAP1 is an intrinsically disordered protein highly expressed by the gastrointestinal epithelium and functions at exposed surfaces to protect the barrier from oxidative insult.

MicroRNA-125a-3p overexpression promotes liver regeneration through targeting proline-rich acidic protein 1

Introduction and objectivesLiver regeneration plays a valuable significance for hepatectomies, and is mainly attributed to hepatocyte proliferation. MicroRNA-125a-3p was reported to be highly associated with liver regeneration process. We studied the underlying mechanism of the functional role of miR-125a-3p in liver regeneration. Materials and methodsThe miR-125a-3p mimics and inhibitor vector were constructed and transfected into primary human liver HL-7702 cells, the transfected cell viability was detected using cell counting kit-8 (CCK-8). Cell cycle distribution was analyzed by flow cytometry. With Targetscan and OUGene prediction, the potential targets of miR-125 were verified by real-time quantitative PCR (qPCR) and luciferase reporter assays in turn. The overexpression vector of proline-rich acidic protein 1 (PRAP1) was constructed and co-transfected with miR-125a-3p mimics into HL-7702 cells, detecting the changes of proliferative capacity and cell cycle distribution. Western blot and qPCR performed to analyze gene expressions. ResultsOverexpressed miR-125a-3p notably increased the hepatocyte viability at 48h, and decreased the number of G1 phase cells (p<0.05). However, miR-125a-3p inhibition suppressed the development of hepatocytes. PRAP1 was the target of miR-125a-3p. After co-transfection with PRAP1 vector, hepatocyte viability was decrease and the G1 phase cell number was increased (p<0.05). More importantly, overexpressed PRAP1 notably decreased the mRNA and protein levels of cyclin D1, cyclin-dependent kinase 2 (CDK2) and cell division cycle 25A (CDC25A). ConclusionThe elevated miR-125a-3p positively correlated with hepatocyte viability and cell cycle progression due to the modulation of PRAP1, and miR-125a-3p may contribute to improving liver regeneration.

Proline-Rich Acidic Protein 1 (PRAP1) is a Target of ARID1A and PGR in the Murine Uterus.

ARID1A and PGR plays an important role in embryo implantation and decidualization during early pregnancy. Uterine specific Arid1a knockout (Pgrcre/+Arid1af/f ) mice exhibit in non-receptive endometrium at day 3.5 of gestation (GD 3.5). In previous studies, using transcriptomic analysis in the uterus of Pgrcre/+Arid1af/f mice, we identified proline-rich acidic protein 1 (PRAP1) as one of the down-regulated genes by ARID1A in the uterus. In the present study, we performed RT-qPCR and immunohistochemistry analysis to investigate the regulation of PRAP1 by ARID1A and determine expression patterns of PRAP1 in the uterus during early pregnancy. During early pregnancy, PRAP1 expression was strong at day 0.5 of gestation (GD 0.5) and then decreased at GD 3.5 in the epithelium and stroma. After implantation, PRAP1 expression was remarkably reduced in the uterus. However, the expression of PRAP1 at GD 3.5 was remarkably increased in the Pgrcre/+Arid1a f/f mice. To determine the ovarian steroid hormone regulation of PRAP1, we examined the expression of PRAP1 in ovariectomized control, Pgrcre/+Arid1af/f , and progesterone receptor knock-out (PRKO) mice treated with progesterone. While PRAP1 proteins were strongly expressed in the luminal and glandular epithelium of control mice treated with vehicle, progesterone treatment suppressed the expression of PRAP1. However, PRAP1 was not suppressed in both the Pgrcre/+Arid1af/f and PRKO mice compared to controls. Our results identified PRAP1 as a novel target of ARID1A and PGR in the murine uterus.

PRAP1: A Novel Epithelial Secreted Protein

Proline rich acidic protein‐1 (PRAP1) is a 17 kDa secreted intrinsically disordered protein encoded in higher chordates with no known function or recognizable sequence homology. In the course of evaluating transcriptional activation in murine gut by members of the Lactobacilli taxon, we found PRAP1 induced in the colon within 4 hours of oral gavage with 108 Lactobacilli. To define the physiological role of PRAP1, we have made polyclonal antibodies, PRAP1 recombinant protein and Prap1 null mice. Measurement of PRAP1 expression by qPCR and western blot reveal PRAP1 expression is highest in the proximal small intestine, and interestingly, in a hormonally dependent manner in uterine endometrial cells of female mice. This expression pattern is consistent with immunofluorescence staining demonstrating high expression of PRAP1 in the enterocytes of the duodenum, goblet cells of the ileum and uterine endometria, as well as in the extracellular space of the corresponding mucosal tissue. Preliminary in vivo data shows Prap1 null mice have increased inflammation in the gastrointestinal tract and uterus, along with increased systemic inflammation. Given the localization of PRAP1, its secretion into the lumen of the small intestine and uterus, and its effect on local and systemic inflammation, we hypothesize that PRAP1 is a novel intrinsically disordered protein that contributes to the intrinsic defenses of mucosal epithelial surfaces.Support or Funding InformationNIH RO1 AI 64462This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Proline‐rich acidic protein 1 (PRAP1) is a novel interacting partner of MAD1 and has a suppressive role in mitotic checkpoint signalling in hepatocellular carcinoma

Loss of mitotic checkpoint of cells contributes to chromosomal instability and leads to carcinogenesis. Mitotic arrest deficient 1 (MAD1) is a key component in mitotic checkpoint signalling. In this study, we identified a novel MAD1 interacting partner, proline-rich acidic protein 1 (PRAP1), using yeast-two hybrid screening, and investigated its role in mitotic checkpoint signalling in hepatocellular carcinoma (HCC). We demonstrated the physical interaction of PRAP1 with MAD1 and of PRAP1 with MAD1 isoform MAD1β, using a co-immunoprecipitation assay. Moreover, stable expression of PRAP1 in mitotic checkpoint-competent HCC cells, BEL-7402 and SMMC-7721, induced impairment of the mitotic checkpoint (p < 0.01), formation of chromosome bridges (p < 0.01) and aberrant chromosome numbers (p < 0.001). Interestingly, ectopic expression PRAP1 in HCC cells led to significant under-expression of MAD1. In human HCC tumours, 40.4% (23/57) of HCCs showed under-expression of PRAP1 protein as compared with their corresponding non-tumorous livers; up-regulation of MAD1 protein was significantly associated with down-regulation of PRAP1 (p = 0.030). Our data revealed that PRAP1 is a protein interacting partner of MAD1 and that PRAP1 is able to down-regulate MAD1 and suppress mitotic checkpoint signalling in HCC.

Abstract 572: Proline-rich acidic protein 1 (PRAP1), a novel mitotic arrest deficient 1 (MAD1) interacting partner, suppresses mitotic checkpoint signaling in hepatocellular carcinoma.

Abstract DNA aneuploidy or chromosomal instability is commonly observed in major types of human cancers, and one of the causes for chromosomal instability is defective mitotic checkpoint signaling in cells. Loss of mitotic checkpoint contributes to chromosomal instability, leading to carcinogenesis. The mitotic checkpoint monitors the status of kinetochore-microtubule attachment and delays the onset of anaphase until all kinetochores have been attached with microtubules. Mitotic arrest deficient 1 (MAD1) is key component in mitotic checkpoint signaling. We previously identified a novel isoform of MAD1, which we named MAD1β (Sze et al. Cancer Res 2008;68:9194-9201). In this study, using yeast-two hybrid screening, we have identified a novel MAD1 interacting partner, proline-rich acidic protein 1 (PRAP1). The function of PRAP1 is largely unknown. Hence, we investigated its role in mitotic checkpoint signaling in hepatocellular carcinoma (HCC). We demonstrated the physical interaction between PRAP1, MAD1 and MAD1β in yeast-two hybrid screening and with co-immunoprecipitation assay. Both MAD1 and MAD1β proteins were co-immunoprecipitated with PRAP1. Moreover, we stably expressed PRAP1 in two HCC cell lines, BEL-7402 and SMMC-7721, which have competent mitotic checkpoints. We observed that stable expression of PRAP1 induced impairment in mitotic checkpoint (P &amp;lt; 0.01). After treatment with either colcemid or nocodazole, the PRAP1-stably expressing BEL-7402 and SMMC-7721 cells showed significantly lower mitotic indices as compared with the corresponding vector control cells. Ectopic expression of PRAP1 also resulted in chromosome bridge formation (P&amp;lt; 0.01) and aberrant chromosome numbers (P &amp;lt; 0.001) in these cell lines. All these cellular changes contributed to chromosomal instability. Interestingly, ectopic expression PRAP1 led to significant underexpression of MAD1 but not MAD1β in HCC cells. Taken altogether, our data indicate that PRAP1 is an interacting partner of MAD1 and may have functions of degrading MAD1 and in turn suppressing mitotic checkpoint signaling in HCC. (This study was partly funded by a Hong Kong Research Grants Council GRF grant [HKU 772608]) Citation Format: Karen MF Sze, Glanice K. Chu, Queenie HY Mak, Irene OL Ng. Proline-rich acidic protein 1 (PRAP1), a novel mitotic arrest deficient 1 (MAD1) interacting partner, suppresses mitotic checkpoint signaling in hepatocellular carcinoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 572. doi:10.1158/1538-7445.AM2013-572

PRAP1 is a novel executor of p53-dependent mechanisms in cell survival after DNA damage

p53 has a crucial role in governing cellular mechanisms in response to a broad range of genotoxic stresses. During DNA damage, p53 can either promote cell survival by activating senescence or cell-cycle arrest and DNA repair to maintain genomic integrity for cell survival or direct cells to undergo apoptosis to eliminate extensively damaged cells. The ability of p53 to execute these two opposing cell fates depends on distinct signaling pathways downstream of p53. In this study, we showed that under DNA damage conditions induced by chemotherapeutic drugs, gamma irradiation and hydrogen peroxide, p53 upregulates a novel protein, proline-rich acidic protein 1 (PRAP1). We identified functional p53-response elements within intron 1 of PRAP1 gene and showed that these regions interact directly with p53 using ChIP assays, indicating that PRAP1 is a novel p53 target gene. The induction of PRAP1 expression by p53 may promote resistance of cancer cells to chemotherapeutic drugs such as 5-fluorouracil (5-FU), as knockdown of PRAP1 increases apoptosis in cancer cells after 5-FU treatment. PRAP1 appears to protect cells from apoptosis by inducing cell-cycle arrest, suggesting that the induction of PRAP1 expression by p53 in response to DNA-damaging agents contributes to cancer cell survival. Our findings provide a greater insight into the mechanisms underlying the pro-survival role of p53 in response to cytotoxic treatments.

Proline-Rich Acidic Protein 1 (PRAP1) as a Marker for Established Uterine Receptivity.

The proline-rich acidic protein 1 (PRAP1) is mainly expressed in the epithelial cells and has been suggested to play an important role in maintaining normal growth homeostasis in epithelial cells. We have examined the expression and regulation of PRAP1 in mouse uterus. In situ hybridization indicates that PRAP1 mRNA is exclusively expressed in the uterine luminal epithelium (LE). In ovariectomized uterus, PRAP1 expression levels can be upregulated by 17β-estradiol treatment and downregulated by progesterone treatment. PRAP1 mRNA has unique temporal expression pattern in the early pregnant mouse uterus. In normal wild type uterus, PRAP1 mRNA is strongly detected in day 0.5 LE (mating night as day 0), disappears in pre-implantation day 3.5 LE, and then is intensively expressed in day 4.5 LE after implantation has initiated. These data indicate that the temporal expression of PRAP1 is associated with the establishment of uterine receptivity. This indication has been further demonstrated in experimentally-induced delayed implantation wild type mouse uterus and Lpar3(-/-) mouse uterus with delayed implantation. Indeed, PRAP1 mRNA is undetectable in the non-receptive uterus in both delayed implantation mouse models. These results suggest that PRAP1 may serve as a marker for the established uterine receptivity. However, the function of PRAP1 in the LE has not been established. (Supported by startup funding from The University of Georgia and funding from the Interdisciplinary Toxicology Program at The University of Georgia.) (poster)

Uterine luminal epithelium–specific proline-rich acidic protein 1 (PRAP1) as a marker for successful embryo implantation

Proline-rich acidic protein 1 mRNA is highly expressed in the uterine luminal epithelium (LE) of day 0.5 mouse uterus, disappears in the preimplantation day 3.5 uterus, and reappears abundantly in the LE after embryo implantation has occurred or upon artificial decidualization. In ovariectomized uterus, Prap1 is down-regulated by P, transiently down-regulated by E(2) treatment for 6 hours, but dramatically induced by E(2) treatment for 3 days.

A new perspective: molecular motifs on oxidized LDL, apoptotic cells, and bacteria are targets for chronic lymphocytic leukemia antibodies

AbstractThe restricted immunoglobulin (Ig) repertoire found in B-cell chronic lymphocytic leukemia (CLL) implies a role for antigen(s) in the leukemogenesis. The nature of the antigens has, however, not been characterized, although examples of autoantigens have been demonstrated. We have analyzed a panel of 28 CLL cell lines and primary cultures, producing monoclonal Ig with different Ig heavy-chain variable region gene usage and mutational status, including several complementarity determining region 3 homology subset members. Using mass-spectrometry, immunoassays, or protein macroarrays, we have discovered novel antigens binding to CLL Igs. These antigens included cytoskeletal proteins vimentin, filamin B, and cofilin-1, but also phosphorylcholine-containing antigens (eg, Streptococcus pneumoniae polysaccharides and oxidized low-density lipoprotein [oxLDL]). Additional new antigens identified were cardiolipin and proline-rich acidic protein-1. Remarkably, these antigens represent molecular motifs exposed on apoptotic cells/blebs and bacteria, and several CLL Igs bound to apoptotic Jurkat cells. In conclusion, these intriguing data, showing a limited target structure recognition, indicate that CD5+ CLL B cells are derived from a cell compartment that produces “natural antibodies,” which may be instrumental in elimination and scavenging of apoptotic cells and pathogenic bacteria.