Differential antibody reactivity and CD4 binding of the mammary tumor marker protein GCDFP-15 from breast cyst and its counterparts from exocrine epithelia

Unraveling Human AQP5-PIP Molecular Interaction and Effect on AQP5 Salivary Glands Localization in SS Patients

Saliva secretion requires effective translocation of aquaporin 5 (AQP5) water channel to the salivary glands (SGs) acinar apical membrane. Patients with Sjögren’s syndrome (SS) display abnormal AQP5 localization within acinar cells from SGs that correlate with sicca manifestation and glands hypofunction. Several proteins such as Prolactin-inducible protein (PIP) may regulate AQP5 trafficking as observed in lacrimal glands from mice. However, the role of the AQP5-PIP complex remains poorly understood. In the present study, we show that PIP interacts with AQP5 in vitro and in mice as well as in human SGs and that PIP misexpression correlates with an altered AQP5 distribution at the acinar apical membrane in PIP knockout mice and SS hMSG. Furthermore, our data show that the protein-protein interaction involves the AQP5 C-terminus and the N-terminal of PIP (one molecule of PIP per AQP5 tetramer). In conclusion, our findings highlight for the first time the role of PIP as a protein controlling AQP5 localization in human salivary glands but extend beyond due to the PIP-AQP5 interaction described in lung and breast cancers.

Identification of Urinary Biomarkers for Exercise-Induced Immunosuppression by iTRAQ Proteomics

Purpose

To identify noninvasive immune biomarkers of exercise-induced immunosuppression using the iTRAQ proteomics technique.

Methods

Fifteen healthy males were recruited and subjected to a four-week incremental treadmill running training program. After each week of training, WBC counts and CD4⁺ and CD8⁺ lymphocytes were measured to monitor the immune function status. iTRAQ proteomics technology was used to identify differential proteins and their characteristics in urine.

Results

Our data showed that the WBC counts, CD4⁺ lymphocytes, and CD4⁺/CD8⁺ ratio decreased by more than 10% after four weeks of training, suggesting exercise-induced immunosuppression. A total of 1854 proteins were identified in urine during the incremental running using the iTRAQ technology. Compared with the urine before training, there were 89, 52, 77, and 148 proteins significantly upregulated and 66, 27, 68, and 114 proteins significantly downregulated after each week, respectively. Among them, four upregulated proteins, SEMG-1, PIP, PDGFRL, and NDPK, increased their abundance with the increased exercise intensity. Bioinformatics analysis indicates that these proteins are involved in stress response and immune function.

Conclusion

Four weeks of incremental treadmill running induced immunosuppression in healthy males. By using iTRAQ proteomics, four proteins in the urine, SEMG-1, PIP, PDGFRL, and NDPK, were found to increase incrementally with the increased exercise intensity, which have the potential to be used as noninvasive immune biomarkers of exercise-induced immunosuppression.

Deficiency of prolactin-inducible protein leads to impaired Th1 immune response and susceptibility to Leishmania major in mice

Although the strategic production of prolactin-inducible protein (PIP) at several ports of pathogen entry into the body suggests it might play a role in host defense, no study has directly implicated it in immunity against any infectious agent. Here, we show for the first time that PIP deficiency is associated with reduced numbers of CD4(+) T cells in peripheral lymphoid tissues and impaired CD4(+) Th1-cell differentiation in vitro. In vivo, CD4(+) T cells from OVA-immunized, PIP-deficient mice showed significantly impaired proliferation and IFN-γ production following in vitro restimulation. Furthermore, PIP-deficient mice were highly susceptible to Leishmani major infection and failed to control lesion progression and parasite proliferation. This susceptibility was associated with impaired NO production and leishmanicidal activity of PIP KO macrophages following IFN-γ and LPS stimulation. Collectively, our findings implicate PIP as an important regulator of CD4(+) Th1-cell-mediated immunity.

Dominant Prostasome Immunogens for Sperm-Agglutinating Autoantibodies of Infertile Men

The presence of naturally occurring anti-sperm antibodies (ASA) is a well-known cause of infertility in men and women, but the antigens for these antibodies are poorly characterized. We have previously shown that prostasomes adhere to sperm cells and that prostasomes are major targets for ASA associated with infertility. These autoantigens have not been characterized. We used 2-dimensional electrophoresis, immunoblotting, and mass-spectrometry to identify the prostasome antigens for these autoantibodies. By these techniques, we revealed that prolactin-inducible protein (PIP) and clusterin were dominant prostasome immunogens for sperm-agglutinating autoantibodies of 20 patients with immunological infertility. PIP was identified by 19 of 20 (95%) patient sera and clusterin by 17 of 20 (85%). In addition, 10 sporadically occurring prostasomal antigens were identified in this context, viz alcohol dehydrogenase [NADP+], annexin I, annexin III, BRCA1-associated ring domain protein 1, heat shock 27-kd protein, isocitrate dehydrogenase, lactoylglutathione lyase, NG,NG-dimethylarginine dimethylaminohydrolase 1, peroxiredoxin 2, and syntenin 1.

Crystal structure of the novel complex formed between zinc alpha2-glycoprotein (ZAG) and prolactin-inducible protein (PIP) from human seminal plasma

This is the first report on the formation of a complex between zinc alpha2-glycoprotein (ZAG) and prolactin-inducible protein (PIP). The complex was purified from human seminal plasma and crystallized using 20% polyethylene glycol 9000 and 5% hexaethylene glycol. The structure of the complex has been determined using X-ray crystallographic method and refined to an R(cryst) of 0.199 (R(free)=0.239). The structure of ZAG is broadly similar to the structure of serum ZAG. The scaffolding of PIP consists of seven beta-strands that are organized in the form of two antiparallel beta-pleated sheets, resulting in the formation of a sandwiched beta-sheet. The amino acid sequence of PIP contains one potential N-glycosylation site at Asn77, and the same is found glycosylated with four sugar residues. The structure of the complex shows that the beta-structure of PIP is ideally aligned with the beta-structure of domain alpha3 of ZAG to form a long interface between two proteins. The proximal beta-strands at the long interface are arranged in an antiparallel manner. There are 12 hydrogen bonds and three salt bridges between ZAG and PIP. At the two ends of vertical interface, two salt bridges are formed between pairs of Lys41-Asp233 and Lys68-Glu229. On the perpendicular interface involving alpha1-alpha2 domains of ZAG and a loop of PIP, another salt bridge is formed. The internal space at the corner of the L-shaped structure is filled with solvent molecules including a carbonate ion. The overall buried area in the complex is approximately 914 A(2), which is considerably higher than the 660 A(2) reported for the class I major histocompatibility complex structures.

Altered distribution of aquaporin 5 and its C-terminal binding protein in the lacrimal glands of a mouse model for Sjögren's syndrome

PURPOSE

To investigate the distribution and expression of aquaporin 5 (AQP5) and its C-terminal binding protein in the apical membrane of the lacrimal glands (LGs) in a mouse model for Sjogren's syndrome (SS).

METHODS

The LGs of NOD mice (mouse model for SS) and ICR mice (normal control) were homogenized and delivered into the affinity columns bound to synthetic AQP5 C-terminal peptide. The eluates were analyzed by electrophoresis and liquid chromatography mass spectrometry/mass spectrometry (LC-MS/MS) techniques.

RESULTS

AQP5 from the NOD mice exhibited the capacity to bind a 21-kDa protein that was lacking in the ICR mice. Instead, ICR mouse expressed a 17-kDa AQP5 binding protein that was absent in LGs of SS. LC-MS/MS analysis revealed these respective proteins to be major urinary protein 4 (MUP4) and prolactin-inducible protein (PIP). The treatment of ICR mice with antisense PIP oligonucleotides decreased immunostaining of AQP5 in the apical membrane.

CONCLUSIONS

These observations suggest that the binding of PIP to the C-terminal portion of AQP5 may cause AQP5 to be transported to the apical membrane of LGs. Correction of the aberrant binding of PIP to the AQP5 C-terminus could normalize AQP5 trafficking to the apical membrane, leading to a treatment for patients with SS.

Increased expression of secretory actin-binding protein on human spermatozoa is associated with poor semen quality

BACKGROUND

Antibodies to human sperm are useful diagnostic reagents for detection of changes in sperm protein expression and their relationship with sperm defects and male infertility. The specificity of Hs-16 monoclonal antibody (mAb) and the localization and frequency of the occurrence of Hs-16-recognized protein on human spermatozoa were investigated.

METHODS

Samples from 30 fertile men with normal spermiograms and 30 men with pathological spermiograms were studied. The specificity of Hs-16 mAb was analysed by the western blotting technique and matrix-assisted laser desorption/ionization mass spectrometry. Indirect immunofluorescence with Hs-16 antibody was used to test sperm ejaculates.

RESULTS

The Hs-16 antibody detected a human sperm and seminal plasma protein, which was determined to be secretory actin-binding protein (SABP). This specificity was also verified by co-localization of SABP and actin on spermatozoa with Hs-16 and anti-actin antibodies, and partial co-localization of these proteins was found. SABP was localized on the sperm tail, mainly in the midpiece of the tail. Other parts of spermatozoa were labelled with lower frequency. A significant difference was found in SABP labelling between men with normal spermiograms and donors with asthenozoospermia or oligoasthenoteratozoospermia (both P < 0.01), and asthenozoospermia versus oligoasthenoteratozoospermia (P < 0.05). Increased expression of SABP was observed in men with pathological spermiograms.

CONCLUSIONS

Hs-16 antibody reacts specifically with SABP. SABP can serve as a marker of defective sperm and may be associated with fertility failure.

[Infiltrating lobular carcinoma of the breast with histiocytoid features: three cases]

Histiocytoid carcinoma of the breast, a cellular variant of invasive breast cancer, is mainly found among infiltrating lobular carcinomas (ILC). It can be easily confused with benign conditions or other mammary tumors also composed of cells with a pink granular to foamy cytoplasm and an eccentric nucleus. We report 3 cases of histiocytoid ILC. Our aim is to discuss recent immunocytochemical data that could suggest a special type of apocrine differentiation of tumor cells, including a diffuse immunoreactivity for GCDFP-15 (Gross Cystic Disease Fluid Protein 15) and a predominant expression of androgen receptor, and to describe the features useful for the differential diagnosis.

Expression of the prolactin-inducible protein (PIP/GCDFP15) gene in benign epithelium and adenocarcinoma of the prostate

Prolactin-inducible protein (PIP), also known as gross cystic disease fluid protein 15, is a predominant secretory protein in various body fluids, including saliva, milk and seminal plasma. Immunohistochemistry of this protein has been exploited as a clinical marker for breast cancer and Paget's disease. This study comparatively examined PIP expression in normal prostate tissues and in adenocarcinomas of the prostate. Quantitative real-time RT-PCR revealed low-level presence (6%) of PIP mRNA in normal prostate tissue in comparison with the seminal vesicle. Indirect immunostaining with monoclonal antibody 3E7 displayed a positive sign for benign epithelium in 8 cases (29.6%) among 27 normal specimens; however, the incidence significantly increased to 56.1% (37/66) in instances involving primary prostate carcinoma tissues of different types. Quantitative RT-PCR also demonstrated that PIP transcript levels in carcinoma regions were significantly higher than corresponding levels in benign regions. These findings conclusively showed that benign prostate epithelium expresses PIP at low levels; in contrast, PIP is over-expressed in carcinomas of the prostate.

Human seminal plasma prolactin-inducible protein is an immunoglobulin G-binding protein

Antisperm antibodies (ASA) are present in 20% of couples seeking treatment for infertility. Antibody-binding proteins in seminal plasma may protect sperm from ASA-induced damage. We have previously isolated several IgG-binding proteins from human seminal plasma using IgG affinity chromatography. Here, we report another such protein which we have identified by amino acid sequencing and confirmed by western blotting to be prolactin-inducible protein (PIP). PIP binds via the Fc fragment of IgG. We have determined the level of PIP in normal seminal plasma to be 3.4 mg/ml (interquartile range 2.0-4.4 mg/ml). We have found there is no difference in the mean level of PIP in seminal plasma from fertile or infertile men regardless of ASA status. PIP was shown to exist in several isoforms in seminal plasma by Western blot. There is a complex pattern of PIP isoform variability in seminal plasma from fertile and infertile men but one multimeric form of PIP was absent from the seminal plasma of men with ASA who were fertile. This may reflect consumption of PIP in these men. The physiological function of PIP remains unknown, but the ability of PIP to bind IgG-Fc suggests PIP may have an immunomodulatory role.

Identification of gp17 glycoprotein and characterization of prostatic acid phosphatase (PAP) and carboxypeptidase E (CPE) fragments in a human seminal plasma fraction interacting with concanavalin A

The decapacitating fraction of human seminal plasma, which strongly interacts with concanavalin A, is constituted by high mannose-type N-linked glycoproteins, most of them of less than 44 kDa. Each component with apparent molecular mass of 30, 18, and 17 kDa respectively, as judged by SDS-PAGE, was submitted to "in gel" digestion with trypsin followed by HPLC separation of the peptides and sequencing. They were characterized at microscale as gp17, an aspartyl protease that possibly contributes to liquefaction of the seminal plasma coagulum, two fragments of human acid phosphatase (17 and 30 kDa, respectively), and a 17-kDa fragment of carboxypeptidase E. Neither the fragments of prostatic acid phosphatase nor that of carboxypeptidase E had been described before in the human seminal fluid. Very weak bands, of apparent molecular masses 44 and 52 kDa, are consistent with presence of small amounts of parent compounds, prostatic acid phosphatase and carboxypeptidase E.

Structural study of GCDFP-15/gp17 in disease versus physiological conditions using a proteomic approach

Gross cystic disease fluid protein (GCDFP-15), also known as prolactin-inducible protein (PIP), is a specific breast tumor marker. GCDFP-15/PIP is also identified as gp17 and/or seminal actin-binding protein (SABP) from seminal vesicles and as extraparotid glycoprotein (EP-GP) from salivary glands. It is an aspartyl proteinase able to specifically cleave fibronectin (FN), suggesting a possible involvement in mammary tumor progression and fertilization. Other functions were attributed to this protein(s) on the basis of its ability to interact with an array of molecules such as CD4, actin, and fibrinogen. We investigated the structure of the protein(s) under disease versus physiological conditions by RP-HPLC chromatography, ProteinChip technology, and QStar MS/MS mass spectrometry. The proteins behaved differently when examined by RP-HPLC chromatography and surface-enhanced laser desorption ionization time-of-flight (SELDI-TOF) mass spectrometry, suggesting different conformations and/or tissue-specific posttranslational modifications of the proteins, although their primary structure was identical by MS/MS analysis. Both showed a single N-glycosylation site. A different N-linked glycosylation pattern was observed in pathological GCDFP-15/PIP as compared with physiological gp17/SABP protein by coupling enzymatic digestion and ProteinChip technology. Furthermore, taking advantage of ProteinChip technology, we analyzed the interaction of both proteins with CD4 and FN. We observed that the physiological form was mainly involved in the binding to CD4. Moreover, we defined the specific FN binding-domain of this protein. These data suggested that, depending on its conformational state, the protein could differently bind to its various binding molecules and change its function(s) in the microenviroments where it is expressed.

Identification of a new subset of cells exhibiting dendritic phenotypes in patients affected by breast proliferative disorders

We report that a subset of circulating cells reacting with a monoclonal antibody raised against a protein marker is significantly increased in the peripheral blood of women carrying benign or malignant breast diseases, particularly in patients under 55 years of age with ductal mammary carcinomas. These cells were statistically (confidence level of 99%) less represented in a control population including healthy women or women carrying carcinomas of origin other than breast. Double staining analysis showed that they harbor markers of dendritic cells and exhibit endo- cytic activity, as determined by their ability to internalize FITC-dextran particles. Their dendritic morphology was further demonstrated by electron microscopy of sorted antibody-positive cells. However, expression of surface molecules, such as CD34 and CD14, usually not present in differentiated populations of dendritic cells was also observed. Adherent cells of patients with breast ductal carcinoma including mostly cells of this new subset were efficient stimulators of mixed lymphocyte reaction, attaining maximal stimulatory activity attained after TNFalpha treatment. In conclusion, we have shown that a subset of cells characterized by a phenotype suggestive of a yet undescribed stage of maturation of the dendritic cell lineage is accumulated in the blood of patients affected by breast proliferative disorders.

Mapping the CD4 binding domain of gp17, a glycoprotein secreted from seminal vesicles and breast carcinomas

gp17, a secretory CD4-binding factor isolated from the human seminal plasma, is identical to the gross cystic disease fluid protein-15, a specific marker for primary and metastatic breast tumors. We previously demonstrated that gp17 binds to CD4 with high affinity and strongly inhibits T lymphocyte apoptosis induced by sequential cross-linking of CD4 and T cell receptor (TCR). To further characterize the gp17/CD4 interaction and map the gp17 binding site, we produced a secreted form of recombinant gp17 fused to human IgG1 Fc, gp17-Ig. We showed that gp17-Ig exhibits a binding affinity for CD4 similar to that of native gp17. As no information about gp17 structure is presently available, 99 overlapping gp17 peptides were synthesized by the Spot method, which allowed the mapping of two CD4 binding regions. Alanine scanning of CD4-reactive peptides identified critical residues, selected for site-directed mutagenesis. Nine gp17-Ig mutants were generated and characterized. Three residues within the carboxy-terminal region were identified as the major binding domain to CD4. The Spot method combined with mutagenesis represents a refined approach to distinguish the contact residues from the ones contributing to the conformation of the CD4-binding domain.

A novel aspartyl proteinase from apocrine epithelia and breast tumors

GCDFP-15 (gross cystic disease fluid protein, 15 kDa) is a secretory marker of apocrine differentiation in breast carcinoma. In human breast cancer cell lines, gene expression is regulated by hormones, including androgens and prolactin. The protein is also known under different names in different body fluids such as gp17 in seminal plasma. GCDFP-15/gp17 is a ligand of CD4 and is a potent inhibitor of T-cell apoptosis induced by sequential CD4/T-cell receptor triggering. We now report that GCDFP-15/gp17 is a protease exhibiting structural properties relating it to the aspartyl proteinase superfamily. Unexpectedly, GCDFP-15/gp17 appears to be related to the retroviral members rather than to the known cellular members of this class. Site-specific mutagenesis of Asp(22) (predicted to be catalytically important for the active site) and pepstatin A inhibition confirmed that the protein is an aspartic-type protease. We also show that, among the substrates tested, GCDFP-15/gp17 is specific for fibronectin. The study of GCDFP-15/gp17-mediated proteolysis may provide a handle to understand phenomena as diverse as mammary tumor progression and fertilization.

Circulating antibodies against the breast tumor marker GCDFP-15/gp17 in mammary carcinoma patients and in patients carrying benign breast conditions

Sera samples from 111 women, including 73 breast cancer patients and 38 patients with benign diseases of the breast, were examined. These were compared with samples from healthy women or from patients carrying tumors of origin other than breast as controls. This was done to determine whether antibodies against GCDFP-15/gp17, a protein of gross cystic disease fluid also secreted by mammary apocrine tumor cells, could be found. We observed that 2.6% of mammary disease patients affected by benign conditions and 5.5% of patients carrying malignant mammary gland tumors expressed statistically significant amounts of antibodies against GCDFP-15/gp17 (p < 0.01). The highest circulating anti-GCDFP-15/gp17 antibody levels occurred in patients with highly malignant ductal or lobular carcinoma of the breast and in patients with dysplasia. No correlation was found between the presence of circulating antibodies and the size of the tumor or the age of the patients. A bimodal correlation with the percent of invaded lymph nodes was observed instead. IgM and IgG isotypes were detected among the circulating anti-GCDFP-15/gp17 antibodies, suggesting the involvement of a T-cell-mediated immunoresponse. Our findings raise the possibility that the anti-GCDFP-15/gp17 immune response may be useful as a tool for investigating some aspects of the mechanisms of breast disease progression and that GCDFP-15/gp17 may be explored as an antigen for anti-tumor vaccination. Int. J. Cancer (Pred. Oncol.) 84:568-572, 1999.

Survey of the 1998 optical biosensor literature

The utilization of optical biosensors to study molecular interactions continues to expand. In 1998, 384 articles relating to the use of commercial biosensors were published in 130 different journals. While significant strides in new applications and methodology were made, a majority of the biosensor literature is of rather poor quality. Basic information about experimental conditions is often not presented and many publications fail to display the experimental data, bringing into question the credibility of the results. This review provides suggestions on how to collect, analyze and report biosensor data.

Biosynthesis and immunobiochemical characterization of gp17/GCDFP-15. A glycoprotein from seminal vesicles and from breast tumors, in HeLa cells and in Pichia pastoris yeast

The gp17 factor is a secretory product of human seminal vesicle cells which binds to CD4 and acts as a potent inhibitor of T lymphocyte apoptosis induced by CD4 crosslinking and subsequent T-cell receptor (TCR) activation. The protein is identical to gross cystic disease fluid protein-15 (GCDFP-15), a breast tumor secretory marker PIP (prolactin inducible protein), a prolactin-controlled and androgen-controlled protein; secretory actin binding protein (SABP), a seminal plasma actin binding protein and extra-parotid glycoprotein (EP-GP), a secretory protein from the salivary gland. The structure of this protein has not yet been elucidated and no biological function has been clearly attributed to date. Expression of recombinant gp17/GCDFP-15 cDNA in bacteria and insect cells leads to the production of a misfolded insoluble protein. In this study, we describe the production of gp17/GCDFP-15 in two different eukaryotic systems, namely HeLa cells and the Pichia pastoris yeast. Using constructs in which gp17/GCDFP-15 was tagged with enhanced green fluorescent protein (EGFP) in various combinations, we observed expression only when the fusion protein was directed to the secretory compartment by the correct signal peptide. The resulting fluorescent protein was inefficiently secreted, thus suggesting that gp17/GCDFP-15 is not appropriately post-translationally processed and/or transported in HeLa cells. The use of the P. pastoris secretory pathway allowed instead the accumulation in the culture medium of a GCDFP-15/gp17 species which retained the ability to bind to CD4 and also most of the biochemical and immunological properties of the native protein. The production of an active recombinant molecule opens the way to correlate the structural properties of this peculiar factor to its ability to bind several proteins, including CD4, and to block CD4-mediated T cell programmed death.