Starvation-inactivated MTOR triggers cell migration via a ULK1-SH3PXD2A/TKS5-MMP14 pathway in ovarian carcinoma

ABBREVIATIONS

AMPK: AMP-activated protein kinase; CHX: cycloheximide; RAD001: everolimus; HBSS: Hanks' balanced salt solution; LC-MS/MS: liquid chromatography-mass spectrometry/mass spectrometry; MMP14: matrix metallopeptidase 14; MTOR: mechanistic target of rapamycin kinase; MAPK: mitogen-activated protein kinase; RB1CC1/FIP200: RB1 inducible coiled-coil 1; PtdIns3P: phosphatidylinositol-3-phosphate; PX: phox homology; SH3: Src homology 3; SH3PXD2A/TKS5: SH3 and PX domains 2A; SH3PXD2A-[6A]: S112A S142A S146A S147A S175A S348A mutant; ULK1: unc-51 like autophagy activating kinase 1.

Glycogen synthase kinase-3 beta (GSK3β)-mediated phosphorylation of ETS1 promotes progression of ovarian carcinoma

ETS1 - an evolutionarily conserved transcription factor involved in the regulation of a number of cellular processes - is overexpressed in several malignancies, including ovarian cancer. Most studies on ETS1 expression have been focused on the transcriptional and RNA levels, with post-translational control mechanisms remaining relatively unexplored in the pathogenesis of malignancies. Here, we show that ETS1 forms a complex with glycogen synthase kinase-3β (GSK3β). Specifically, GSK3β-mediated phosphorylation of ETS1 at threonine 265 and serine 269 promoted protein stability, induced the transcriptional activation of matrix metalloproteinase (MMP)-9, and increased cell migration. In vivo experiments revealed that a GSK3β inhibitor was able to suppress both endogenous ETS1 expression and induction of MMP-9 expression. Upon generation of a specific antibody against phosphorylated ETS1, we demonstrated that phospho-ETS1 immunohistochemical expression in ovarian cancer specimens was correlated with that of MMP-9. Notably, the cumulative overall survival of patients with low phospho-ETS1 histoscores was significantly longer than that of those showing higher scores. We conclude that the GSK3β/ETS1/MMP-9 axis may regulate the biological aggressiveness of ovarian cancer and can serve as a prognostic factor in patients with this malignancy.

Integrated genomic analyses in PDX model reveal a cyclin-dependent kinase inhibitor Palbociclib as a novel candidate drug for nasopharyngeal carcinoma

Background

Patient-derived xenograft (PDX) tumor model has become a new approach in identifying druggable tumor mutations, screening and evaluating personalized cancer drugs based on the mutated targets.

Methods

We established five nasopharyngeal carcinoma (NPC) PDXs in mouse model. Subsequently, whole-exome sequencing (WES) and genomic mutation analyses were performed to search for genetic alterations for new drug targets. Potential drugs were applied in two NPC PDX mice model to assess their anti-cancer activities. RNA sequencing and transcriptomic analysis were performed in one NPC PDX mice to correlate with the efficacy of the anti-cancer drugs.

Results

A relative high incident rate of copy number variations (CNVs) of cell cycle-associated genes. Among the five NPC-PDXs, three had cyclin D1 (CCND1) amplification while four had cyclin-dependent kinase inhibitor CDKN2A deletion. Furthermore, CCND1 overexpression was observed in > 90% FFPE clinical metastatic NPC tumors (87/91) and was associated with poor outcomes. CNV analysis disclosed that plasma CCND1/CDKN2A ratio is correlated with EBV DNA load in NPC patients’ plasma and could serve as a screening test to select potential CDK4/6 inhibitor treatment candidates. Based on our NPC PDX model and RNA sequencing, Palbociclib, a cyclin-dependent kinase inhibitor, proved to have anti-tumor effects by inducing G1 arrest. One NPC patient with liver metastatic was treated with Palbociclib, had stable disease response and a drop in Epstein Barr virus (EBV) EBV titer.

Conclusions

Our integrated information of sequencing-based genomic studies and tumor transcriptomes with drug treatment in NPC-PDX models provided guidelines for personalized precision treatments and revealed a cyclin-dependent kinase inhibitor Palbociclib as a novel candidate drug for NPC.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0873-5) contains supplementary material, which is available to authorized users.

Variability Assessment of 90 Salivary Proteins in Intraday and Interday Samples from Healthy Donors by Multiple Reaction Monitoring-Mass Spectrometry

PURPOSE

Saliva is an attractive sample source for the biomarker-based testing of several diseases, especially oral cancer. Here, we sought to apply multiplexed LC-MRM-MS to precisely quantify 90 disease-related proteins and assess their intra- and interindividual variability in saliva samples from healthy donors.

EXPERIMENTAL DESIGN

We developed two multiplexed LC-MRM-MS assays for 122 surrogate peptides representing a set of disease-related proteins. Saliva samples were collected from 10 healthy volunteers at three different time points (Day 1 morning and afternoon, and Day 2 morning). Each sample was spiked with a constant amount of a ¹⁵ N-labeled protein and analyzed by MRM-MS in triplicate. Quantitative results from LC-MRM-MS were calculated by single-point quantification with reference to a known amount of internal standard (heavy peptide).

RESULTS

The CVs for assay reproducibility and technical variation were 13 and 11%, respectively. The average concentrations of the 99 successfully quantified proteins ranged from 0.28 ± 0.58 ng mL^-1 for profilin-2 (PFN2) to 8.55 ±8.96 μg mL^-1 for calprotectin (S100A8). For the 90 proteins detectable in >50% of samples, the average CVs for intraday, interday, intraindividual, and interindividual samples were 38%, 43%, 45%, and 69%, respectively. The fluctuations of most target proteins in individual subjects were found to be within ± twofold.

CONCLUSIONS AND CLINICAL RELEVANCE

Our study elucidated the intra- and interindividual variability of 90 disease-related proteins in saliva samples from healthy donors. The findings may facilitate the further development of salivary biomarkers for oral and systemic diseases.

Argininosuccinate synthetase 1 contributes to gastric cancer invasion and progression by modulating autophagy

Argininosuccinate synthetase 1 (ASS1) is a rate-limited enzyme in arginine biosynthesis. The oncogenic potential of ASS1 in terms of prognosis and cancer metastasis in arginine prototrophic gastric cancer (GC) remains unclear at present. We identify differentially expressed proteins in microdissected GC tumor cells relative to adjacent nontumor epithelia by isobaric mass tag for relative and absolute quantitation proteomics analysis. GC cells with stable expression or depletion of ASS1 were further analyzed to identify downstream molecules. We investigated their effects on chemoresistance and cell invasion in the presence or absence of arginine. ASS1 was highly expressed in GC and positively correlated with GC aggressiveness and poor outcome. Depletion of ASS1 led to inhibition of tumor growth and decreased cell invasion via induction of autophagy-lysosome machinery, resulting in degradation of active β-catenin, Snail, and Twist. Ectopic expression of ASS1 in GC cells reversed these effects and protected cancer cells from chemotherapy drug-induced apoptosis via activation of the AKT-mammalian target of rapamycin signaling pathway. ASS1 contributes to GC progression by enhancing aggressive potential resulting from active β-catenin, Snail, and Twist accumulation. Our results propose that ASS1 might contribute to GC metastasis and support its utility as a prognostic predictor of GC.-Tsai, C.-Y., Chi, H.-C., Chi, L.-M., Yang, H.-Y., Tsai, M.-M., Lee, K.-F., Huang, H.-W., Chou, L.-F., Cheng, A.-J., Yang, C.-W., Wang, C.-S., Lin, K.-H. Argininosuccinate synthetase 1 contributes to gastric cancer invasion and progression by modulating autophagy.

Development of a Multiplexed Assay for Oral Cancer Candidate Biomarkers Using Peptide Immunoaffinity Enrichment and Targeted Mass Spectrometry

Oral cancer is one of the most common cancers worldwide, and there are currently no biomarkers approved for aiding its management. Although many potential oral cancer biomarkers have been discovered, very few have been verified in body fluid specimens in parallel to evaluate their clinical utility. The lack of appropriate multiplexed assays for chosen targets represents one of the bottlenecks to achieving this goal. In the present study, we develop a peptide immunoaffinity enrichment-coupled multiple reaction monitoring-mass spectrometry (SISCAPA-MRM) assay for verifying multiple reported oral cancer biomarkers in saliva. We successfully produced 363 clones of mouse anti-peptide monoclonal antibodies (mAbs) against 36 of 49 selected targets, and characterized useful mAbs against 24 targets in terms of their binding affinity for peptide antigens and immuno-capture ability. Comparative analyses revealed that an equilibrium dissociation constant (K_D ) cut-off value < 2.82 × 10^-9 m could identify most clones with an immuno-capture recovery rate >5%. Using these mAbs, we assembled a 24-plex SISCAPA-MRM assay and optimized assay conditions in a 25-μg saliva matrix background. This multiplexed assay showed reasonable precision (median coefficient of variation, 7.16 to 32.09%), with lower limits of quantitation (LLOQ) of <10, 10-50, and >50 ng/ml for 14, 7 and 3 targets, respectively. When applied to a model saliva sample pooled from oral cancer patients, this assay could detect 19 targets at higher salivary levels than their LLOQs. Finally, we demonstrated the utility of this assay for quantification of multiple targets in individual saliva samples (20 healthy donors and 21 oral cancer patients), showing that levels of six targets were significantly altered in cancer compared with the control group. We propose that this assay could be used in future studies to compare the clinical utility of multiple oral cancer biomarker candidates in a large cohort of saliva samples.

Association of anticardiolipin, antiphosphatidylserine, anti-β2 glycoprotein I, and antiphosphatidylcholine autoantibodies with canine immune thrombocytopenia

Background

In humans, the presence of antiphospholipid antibodies (aPL) is frequently found in immune thrombocytopenia. The present study investigated whether aPL and any aPL subtypes are associated with canine thrombocytopenia, in particular, immune-mediated thrombocytopenia (immune thrombocytopenia) that usually manifests with severe thrombocytopenia.

Results

Sera were collected from 64 outpatient dogs with thrombocytopenia (Group I, platelet count 0 – 80 × 10³/uL), and 38 of which having severe thrombocytopenia (platelet count < 30 × 10³/uL) were further divided into subgroups based on the presence of positive antiplatelet antibodies (aPLT) (subgroup I_A, immune thrombocytopenia, n =20) or the absence of aPLT (subgroup I_B, severe thrombocytopenia negative for aPLT, n =18). In addition, sera of 30 outpatient dogs without thrombocytopenia (Group II), and 80 healthy dogs (Group III) were analyzed for comparison. Indirect ELISAs were performed to compare serum levels of aPL subtypes, including anticardiolipin antibodies (aCL), antiphosphatidylserine antibodies (aPS), antiphosphatidylcholine (aPC), and anti-β₂ glycoprotein I antibodies (aβ₂GPI), and antiphosphatidylinositol antibodies (aPI), among different groups or subgroups of dogs. Among outpatient dogs, aCL, being highly prevalent in outpatient dogs with thrombocytopenia (63/64, 98 %), is an important risk factor for thrombocytopenia (with a high relative risk of 8.3), immune thrombocytopenia (relative risk 5.3), or severe thrombocytopenia negative for aPLT (relative risk ∞, odds ratio 19). In addition, aPS is a risk factor for immune thrombocytopenia or severe thrombocytopenia negative for aPLT (moderate relative risks around 2), whereas aPC and aβ₂GPI are risk factors for immune thrombocytopenia (relative risks around 2).

Conclusions

Of all the aPL subtypes tested here, aCL is highly associated with canine thrombocytopenia, including immune thrombocytopenia, severe thrombocytopenia negative for aPLT, and less severe thrombocytopenia. Furthermore, aPS is moderately associated with both canine immune thrombocytopenia and severe thrombocytopenia negative for aPLT, whereas aβ₂GPI, and aPC are moderately relevant to canine immune thrombocytopenia. In contrast, aPI is not significantly associated with canine immune thrombocytopenia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0727-3) contains supplementary material, which is available to authorized users.

MicroRNA-205 targets tight junction-related proteins during urothelial cellular differentiation

The mammalian bladder urothelium classified as basal, intermediate, and terminally differentiated umbrella cells offers one of the most effective permeability barrier functions known to exist in nature because of the formation of apical uroplakin plaques and tight junctions. To improve our understanding of urothelial differentiation, we analyzed the microRNA (miRNA) expression profiles of mouse urinary tissues and by TaqMan miRNA analysis of microdissected urothelial layers and in situ miRNA-specific hybridization to determine the dependence of these miRNAs on the differentiation stage. Our in situ hybridization studies revealed that miR-205 was enriched in the undifferentiated basal and intermediate cell layers. We then used a quantitative proteomics approach to identify miR-205 target genes in primary cultured urothelial cells subjected to antagomir-mediated knockdown of specific miRNAs. Twenty-four genes were reproducibly regulated by miR-205; eleven of them were annotated as cell junction- and tight junction-related molecules. Western blot analysis demonstrated that antagomir-induced silencing of miR-205 in primary cultured urothelial cells elevated the expression levels of Tjp1, Cgnl1, and Cdc42. Ectopic expression of miR-205 in MDCK cells inhibited the expression of tight junction proteins and the formation of tight junctions. miR-205- knockdown urothelial cells showed alterations in keratin synthesis and increases of uroplakin Ia and Ib, which are the urothelial differentiation products. These results suggest that miR-205 may contribute a role in regulation of urothelial differentiation by modulating the expression of tight junction-related molecules.

Overexpression of BST2 is associated with nodal metastasis and poorer prognosis in oral cavity cancer

OBJECTIVES/HYPOTHESIS

Bone marrow stromal cell antigen 2 (BST2) was one of the proteins that were found to be related to tumor metastasis in our previous proteomic study. Now we examine its clinical role on the oral cavity squamous cell carcinoma (OSCC).

STUDY DESIGN

Individual retrospective cohort study and basic research.

METHODS

Immunohistochemical analysis, Western blotting, and quantitative real-time polymerase chain reaction were used to demonstrate the expression levels of BST2 on 159 OSCC tumors. RNA interference was utilized for cell migration and proliferation study in vitro.

RESULTS

BST2 expression was significantly higher in OSCC cells of metastatic lymph nodes and primary tumor cells, compared to adjacent normal epithelia. Higher BST2 expression was associated with positive N stage, advanced overall stage, perineural invasion, and tumor depth (P = .049, .015, .021, and .010, respectively). OSCC patients with higher BST2 expression had poorer prognosis for disease-specific and disease-free survival (P = .009 and .001, respectively). Multivariate analyses also demonstrated that higher BST2 expression is an independent prognostic factor of disease-specific and disease-free survival (P = .047 and .013, respectively). In vitro suppression of BST2 expression in OEC-M1 cells showed that BST2 contributes to tumor migration of OSCC cells.

CONCLUSIONS

The findings in this study indicate that BST2 expression in OSCC tumors is an independent prognostic factor of patient survival and associated with tumor metastasis.

Genomic and cDNA Cloning, Characterization ofDelonix regiaTrypsin Inhibitor (DrTI) Gene, and Expression of DrTI inEscherichia coli

Degenerate primers were designed based on all possible sequences of the N-terminal and C-terminal regions of Delonix regia trypsin inhibitor (DrTI). Five hundred sixty-one bp of polymerase chain reaction (PCR) product was amplified using the above degenerate primers and genomic DNA and cDNA of Delonix regia as a template. The amplified PCR products were cloned and sequenced. DNA sequence analysis of cDNA and genomic clones of DrTI have the same nucleotide sequence in the coding region, and manifested a genomic clone without intervening sequences in the coding region. The amino acid sequence deduced from the DrTI genomic and cDNA clones agreed with that identified via amino acid sequencing analysis, except that two amino acid residues, Ser and Lys, existed between residues Lys141 and Ser142. DrTI open reading frame was then amplified and cloned in-frame with GST in pGEX4T-1 and overexpressed in Escherichia coli to yield a glutathione S-transferase (GST)-fusion protein with a calculated molecular mass of about 45 kDa. The recombinant DrTI (reDrTI) was derived by treating the GST-DrTI fusion protein with thrombin. Both the reDrTI and GST-DrTI fusion protein exhibited a strong identical inhibitory effect on trypsin activity.

Low-molecular-mass secretome profiling identifies C-C motif chemokine 5 as a potential plasma biomarker and therapeutic target for nasopharyngeal carcinoma

Cancer cell secretome profiling has been shown to be a promising strategy for identifying potential body fluid-accessible cancer biomarkers and therapeutic targets. However, very few reports have investigated low-molecular-mass (LMr) proteins (<15kDa) in the cancer cell secretome. In the present study, we applied tricine-SDS-gel-assisted fractionation in conjunction with LC-MS/MS to systemically identify LMr proteins in the secretomes of three nasopharyngeal carcinoma (NPC) cell lines. We examined two NPC tissue transcriptome datasets to identify LMr genes/proteins that are highly upregulated in NPC tissues and also secreted/released from NPC cells, obtaining 35 candidates. We verified the overexpression of four targets (LSM2, SUMO1, RPL22, and CCL5) in NPC tissues by immunohistochemistry and demonstrated elevated plasma levels of two targets (S100A2 and CCL5) in NPC patients by ELISA. Notably, plasma CCL5 showed good power (AUC 0.801) for discriminating NPC patients from healthy controls. Additionally, functional assays revealed that CCL5 promoted migration of NPC cells, an effect that was effectively blocked by CCL5-neutralizing antibodies and maraviroc, a CCL5 receptor antagonist. Collectively, our data indicate the feasibility of the tricine-SDS-gel/LC-MS/MS approach for efficient identification of LMr proteins from cancer cell secretomes, and suggest that CCL5 is a potential plasma biomarker and therapeutic target for NPC.

BIOLOGICAL SIGNIFICANCE

Both LMr proteome and cancer cell secretome represent attractive reservoirs for discovery of cancer biomarkers and therapeutic targets. Our present study provides evidence for the practicality of using the tricine-SDS-PAGE/LC-MS/MS approach for in-depth identification of LMr proteins from the NPC cell secretomes, leading to the discovery of CCL5 as a potential plasma biomarker and therapeutic target for NPC. We believe that the modified GeLC-MS/MS approach used here can be further applied to explore extremely low-abundance, extracellular LMr proteins with important biological functions in other cell lines and biospecimens.

Identification of the lamin A/C phosphoepitope recognized by the antibody P-STM in mitotic HeLa S3 cells

Background

Lamins A and C, two major structural components of the nuclear lamina that determine nuclear shape and size, are phosphoproteins. Phosphorylation of lamin A/C is cell cycle-dependent and is involved in regulating the assembly–disassembly of lamin filaments during mitosis. We previously reported that P-STM, a phosphoepitope-specific antibody raised against the autophosphorylation site of p21-activated kinase 2, recognizes a number of phosphoproteins, including lamins A and C, in mitotic HeLa cells.

Results

Here, using recombinant proteins and synthetic phosphopeptides containing potential lamin A/C phosphorylation sites in conjunction with in vitro phosphorylation assays, we determined the lamin A/C phosphoepitope(s) recognized by P-STM. We found that phosphorylation of Thr-19 is required for generating the P-STM phosphoepitope in lamin A/C and showed that it could be created in vitro by p34^cdc2/cyclin B kinase (CDK1)-catalyzed phosphorylation of lamin A/C immunoprecipitated from unsynchronized HeLa S3 cells. To further explore changes in lamin A/C phosphorylation in living cells, we precisely quantified the phosphorylation levels of Thr-19 and other sites in lamin A/C isolated from HeLa S3 cells at interphase and mitosis using the SILAC method and liquid chromatography-tandem mass spectrometry. The results showed that the levels of phosphorylated Thr-19, Ser-22 and Ser-392 in both lamins A and C, and Ser-636 in lamin A only, increased ~2- to 6-fold in mitotic HeLa S3 cells.

Conclusions

Collectively, our results demonstrate that P-STM is a useful tool for detecting Thr-19-phosphorylated lamin A/C in cells and reveal quantitative changes in the phosphorylation status of major lamin A/C phosphorylation sites during mitosis.

Abstract 3394: Identification of PRDX4 and P4HA2 as metastasis-associated proteins in oral cavity squamous cell carcinoma by comparative tissue proteomics of microdissected specimens using iTRAQ technology

Background Cervical lymph node metastasis represents the major prognosticator for oral cavity squamous cell carcinoma (OSCC). Methods Here, we used an iTRAQ-based quantitative proteomic approach to identify proteins that are differentially expressed between microdissected primary and metastatic OSCC tumors. The selected candidates were examined in tissue sections via immunohistochemistry, and their roles in OSCC cell function investigated using RNA interference. Results Seventy-four differentially expressed proteins in nodal metastases, including PRDX4 and P4HA2, were identified. Immunohistochemical analysis revealed significantly higher levels of PRDX4 and P4HA2 in tumor cells than adjacent non-tumor epithelia (P &lt; 0.0001 and P &lt; 0.0001, respectively), and even higher expression in the 31 metastatic tumors of lymph nodes, compared to the corresponding primary tumors (P = 0.060 and P &lt; 0.0001, respectively). Overexpression of PRDX4 and P4HA2 was significantly associated with positive pN status (P = 0.048 and P = 0.041, respectively). PRDX4 overexpression was a significant prognostic factor for disease-specific survival in both univariate and multivariate analyses (P = 0.034 and P = 0.032, respectively). Additionally, cell migration and invasiveness were attenuated in OEC-M1 cells upon in vitro knockdown of PRDX4 and P4HA2 with specific interfering RNA. Conclusions Novel metastasis-related prognostic markers for OSCC could be identified by our approach.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3394. doi:1538-7445.AM2012-3394

Stable isotope labeling with amino acids in cell culture (SILAC)-based quantitative proteomics study of a thyroid hormone-regulated secretome in human hepatoma cells

The thyroid hormone, 3, 3',5-triiodo-l-thyronine (T(3)), regulates cell growth, development, differentiation, and metabolism via interactions with thyroid hormone receptors (TRs). However, the secreted proteins that are regulated by T(3) are yet to be characterized. In this study, we used the quantitative proteomic approach of stable isotope labeling with amino acids in cell culture coupled with nano-liquid chromatography-tandem MS performed on a LTQ-Orbitrap instrument to identify and characterize the T(3)-regulated proteins secreted in human hepatocellular carcinoma cell lines overexpressing TRα1 (HepG2-TRα1). In total, 1742 and 1714 proteins were identified and quantified, respectively, in three independent experiments. Among these, 61 up-regulated twofold and 11 down-regulated twofold proteins were identified. Eight proteins displaying increased expression and one with decreased expression in conditioned media were validated using Western blotting. Real-time quantitative RT-PCR further disclosed induction of plasminogen activator inhibitor-1 (PAI-1), a T(3) target, in a time-course and dose-dependent manner. Serial deletions of the PAI-1 promoter region and subsequent chromatin immunoprecipitation assays revealed that the thyroid hormone response element on the promoter is localized at positions -327/-312. PAI-1 overexpression enhanced tumor growth and migration in a manner similar to what was seen when T(3) induced PAI-1 expression in J7-TRα1 cells, both in vitro and in vivo. An in vitro neutralizing assay further supported a crucial role of secreted PAI-1 in T(3)/TR-regulated cell migration. To our knowledge, these results demonstrate for the first time that proteins involved in the urokinase plasminogen activator system, including PAI-1, uPAR, and BSSP4, are augmented in the extra- and intracellular space of T(3)-treated HepG2-TRα1 cells. The T(3)-regulated secretome generated in the current study may provide an opportunity to establish the mechanisms underlying T(3)-associated tumor progression and prognosis.

Identification of PRDX4 and P4HA2 as metastasis-associated proteins in oral cavity squamous cell carcinoma by comparative tissue proteomics of microdissected specimens using iTRAQ technology

Cervical lymph node metastasis represents the major prognosticator for oral cavity squamous cell carcinoma (OSCC). Here, we used an iTRAQ-based quantitative proteomic approach to identify proteins that are differentially expressed between microdissected primary and metastatic OSCC tumors. The selected candidates were examined in tissue sections via immunohistochemistry, and their roles in OSCC cell function investigated using RNA interference. Seventy-four differentially expressed proteins in nodal metastases, including PRDX4 and P4HA2, were identified. Immunohistochemical analysis revealed significantly higher levels of PRDX4 and P4HA2 in tumor cells than adjacent non-tumor epithelia (P < 0.0001 and P < 0.0001, respectively), and even higher expression in the 31 metastatic tumors of lymph nodes, compared to the corresponding primary tumors (P = 0.060 and P = 0.002, respectively). Overexpression of PRDX4 and P4HA2 was significantly associated with positive pN status (P = 0.048 and P = 0.021, respectively). PRDX4 overexpression was a significant prognostic factor for disease-specific survival in both univariate and multivariate analyses (P = 0.034 and P = 0.032, respectively). Additionally, cell migration and invasiveness were attenuated in OEC-M1 cells upon in vitro knockdown of PRDX4 and P4HA2 with specific interfering RNA. Novel metastasis-related prognostic markers for OSCC could be identified by our approach.

Identification of guanylate-binding protein 1 as a potential oral cancer marker involved in cell invasion using omics-based analysis

Oral cavity squamous cell carcinoma (OSCC) is a devastating disease that accounts for 3% of all cancer cases diagnosed annually. OSCC is usually diagnosed at advanced clinical stages, resulting in poor outcomes. To identify effective biomarkers for improved OSCC diagnosis and/or management, we simultaneously analyzed the OSCC cell secretome and tissue transcriptome. Among the 19 candidates isolated, guanylate-binding protein 1 (GBP1) was selected for further validation using serum samples from OSCC patients and healthy controls. Notably, the serum level of GBP1 was higher in OSCC patients, compared to that in healthy controls. Immunohistochemical analysis further revealed GBP1 overexpression in OSCC tissues, compared with adjacent noncancerous epithelia. Importantly, the higher GBP1 level in OSCC tissue was associated with higher overall pathological stage, positive perineural invasion, and poorer prognosis. Moreover, GBP1 modulated the migration and invasion of OSCC cells in vitro. Our results collectively indicate that integrated analysis of the cancer secretome and transcriptome is a feasible strategy for the efficient identification of novel OSCC markers.

Elevated amniotic fluid F₂-isoprostane: a potential predictive marker for preeclampsia

In the complex mechanism of preeclampsia, oxidative stress is an important pathogenic factor, and F₂-isoprostane is a marker of oxidative stress and lipid peroxidation. The objective of this study was to identify if the amniotic fluid (AF) levels of F₂-isoprostanes were elevated in women who later developed preeclampsia. In this study, we analyzed AF F₂-isoprostane concentrations with enzyme immunoassay (EIA), and the EIA results could be validated by quantitative mass spectrometry. The mean AF concentration of F₂-isoprostanes was significantly higher in pregnancies with subsequent development of preeclampsia (123.1 ± 57.6 pg/ml, n = 85) than in controls (73.8 ± 36.6 pg/ml, n = 85). The AF elevation of F₂-isoprostanes was even higher in the preeclampsia with intrauterine growth restriction group (138.3 ± 65.2 pg/ml, n = 39). The area under the curve of the receiver operating characteristics analysis for AF F₂-isoprostanes assay was 0.81, supporting its potential as a biomarker for preeclampsia. These results indicate that oxidative stress existed before the onset of clinical preeclampsia, further suggesting that the elevation of AF F₂-isoprostanes may be used as a guide for antioxidant supplementation to reduce the risk and/or severity of preeclampsia.

Enhanced interferon signaling pathway in oral cancer revealed by quantitative proteome analysis of microdissected specimens using 16O/18O labeling and integrated two-dimensional LC-ESI-MALDI tandem MS

Oral squamous cell carcinoma (OSCC) remains one of the most common cancers worldwide, and the mortality rate of this disease has increased in recent years. No molecular markers are available to assist with the early detection and therapeutic evaluation of OSCC; thus, identification of differentially expressed proteins may assist with the detection of potential disease markers and shed light on the molecular mechanisms of OSCC pathogenesis. We performed a multidimensional (16)O/(18)O proteomics analysis using an integrated ESI-ion trap and MALDI-TOF/TOF MS system and a computational data analysis pipeline to identify proteins that are differentially expressed in microdissected OSCC tumor cells relative to adjacent non-tumor epithelia. We identified 1233 unique proteins in microdissected oral squamous epithelia obtained from three pairs of OSCC specimens with a false discovery rate of <3%. Among these, 977 proteins were quantified between tumor and non-tumor cells. Our data revealed 80 dysregulated proteins (53 up-regulated and 27 down-regulated) when a 2.5-fold change was used as the threshold. Immunohistochemical staining and Western blot analyses were performed to confirm the overexpression of 12 up-regulated proteins in OSCC tissues. When the biological roles of 80 differentially expressed proteins were assessed via MetaCore analysis, the interferon (IFN) signaling pathway emerged as one of the most significantly altered pathways in OSCC. As many as 20% (10 of 53) of the up-regulated proteins belonged to the IFN-stimulated gene (ISG) family, including ubiquitin cross-reactive protein (UCRP)/ISG15. Using head-and-neck cancer tissue microarrays, we determined that UCRP is overexpressed in the majority of cheek and tongue cancers and in several cases of larynx cancer. In addition, we found that IFN-beta stimulates UCRP expression in oral cancer cells and enhances their motility in vitro. Our findings shed new light on OSCC pathogenesis and provide a basis for the future development of novel biomarkers.

A missense polymorphism in porcine interferon-gamma cDNA affects antiviral activity of the protein variant

We determined the interferon-γ (IFN-γ) cDNA sequence from three porcine breeds, Duroc, Landrance/Duroc hybrid, and Landrance breeds. Five single nucleotide polymorphisms (SNPs) of porcine IFN-γ (PoIFN-γ) were identified, respectively, at positions 269 (A/G), 376 (C/T), 426 (T/C), and 465 (T/C) of the coding sequence in Landrance/Duroc hybrid, and at position 251 (A/G) in Landrance breed. Among them, A269G and A251G polymorphisms resulted in Q67R and K61R replacements in the mature protein. PoIFN-γ cDNAs of Duroc breed (PoIFN-γ-W) and Landrance/Duroc hybrid (PoIFN-γ-M), which, respectively, encoded Q67 and R67, were introduced into a prokaryotic expression vector pET32 to express recombinant PoIFN-γ-W (rPoIFN-γ-W) and rPoIFN-γ-M protein variants in Escherichia coli. The identity of both protein variants was further confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). We then compared bioactivities of these two recombinant proteins. Although both recombinant protein variants exhibited comparable activities in antiproliferation of PK-15 cells and in nitric oxide (NO) induction of porcine peripheral monocytes, antiviral activity of rPoIFN-γ-W protein was significantly higher (P < 0.001) than that of rPoIFN-γ-M protein in a plaque inhibition assay using pseudorabies virus (PRV). IC50 values of rPoIFN-γ-W and rPoIFN-γ-M protein in anti-PRV assay were determined as 5.3 ± 1.3 and 9.3 ± 4.3 nM, respectively.

In conclusion, we have identified five novel SNPs in PoIFN-γ cDNA, including two missense polymorphisms that result in Q67R and K61R replacements. Our results further demonstrate that Q67R can markedly reduce antiviral activity of the PoIFN-γ protein. This is the first report that shows the functional SNP in the coding region of IFN-γ. In the future, it is imperative to determine whether Q67R replacement in IFN-γ may have disease association.

Selective downregulation of EGF receptor and downstream MAPK pathway in human cancer cell lines by active components partially purified from the seeds of Livistona chinensis R. Brown

Deregulation of protein kinase-mediated signaling events is one of the major causes to malignant transformation. In this work, we tried to purify protein kinase inhibitory activity and antitumor activity from ethanol extracts of the seeds of Livistona chinensis R. Brown (LC), a traditional herb used for the treatment of nasopharyngeal carcinoma (NPC). Both activities were found to be co-purified in various chromatography steps, and a highly purified fraction, LC-X, was obtained and its biological effects were characterized further. LC-X inhibited the activities of various protein kinases in vitro, including PAK2, PKA, PKC, GSK-3alpha, CK2, mitogen-activated protein kinase (MAPK), and JNK1, with IC(50) between approximately 1 and 40microg/ml. The proliferation of two NPC (NPC-TW02 and -TW04) and one breast cancer (MCF-7) cell lines, but not the epidermoid (A431) and cervical (HeLa) carcinoma cell lines, were significantly blocked by LC-X at the dose of >50microg/ml. Cell cycle arrested at G(2)/M phase and apoptosis were detected in NPC-TW02 cells treated with LC-X for 24h. Further studies revealed that epidermal growth factor (EGF)-induced activation of epidermal growth factor receptor (EGFR) and MAPK could be potently inhibited by LC-X in both NPC-TW02 and A431cells in a dose-dependent manner. More interestingly, the level of EGFR protein detected by Western blot decreased drastically in LC-X-treated A431 and NPC-TW02 cells in a dose- and time-dependent fashion. Further analysis of the plasma membrane and cytosolic fractions from LC-X-treated and untreated A431 cells showed that a 170kDa protein selectively disappeared from the plasma membrane of LC-X-treated cells. The protein was identified as EGFR by MALDI-TOF mass spectrometry, indicating EGFR as a selective target for LC-X. Moreover, the electrophoretic mobility of purified EGFR in SDS-PAGE was altered dramatically post LC-X treatment, suggesting that LC-X may chemically modify EGFR. In conclusion, the active components with both antitumor and protein kinases inhibitor activities were highly purified from LC, which can inhibit the EGF signaling events mainly through EGFR modification. Blockage of the functions of EGFR may account for the antitumor activity of these active components.

Identification of a new in vivo phosphorylation site in the cytoplasmic carboxyl terminus of EBV-LMP1 by tandem mass spectrometry

Latent membrane protein 1 (LMP1), an oncogenic protein encoded by Epstein-Barr virus (EBV), has been verified to be phosphorylated in vitro by protein casein kinase 2 (CK2). In this study, we characterized the phosphorylation of the carboxyl terminus of LMP1 fused with glutathione-S-transferase (GST-LMP1c) and the FLAG-epitope-tagged LMP1 (F-LMP1) proteins expressed in HEK293T cells. Using a combination of chemical modification and tandem mass spectrometry, we detected the phosphorylation of a tryptic peptide, 191-223 amino acids, in both GST-LMP1c catalysed by CK2 and F-LMP1-expressing cell lines. Serine residues at positions 211 and 215 were determined to be the substrates of CK2 in vitro. Most importantly, the S215 phosphorylation was also detected in F-LMP1-expressing human cell lines. The phosphorylation of S215, which is located in the carboxyl-terminus activation region 1 of LMP1, provides a new insight for investigating the role and modulation of the phosphorylation of LMP1.

Identification of protein kinase CK2 as a potent kinase of Epstein-Barr virus latent membrane protein 1

The C-terminus of latent membrane protein 1 (LMP1) can be phosphorylated in vivo. However, the protein kinase responsible for LMP1 phosphorylation has not yet been identified. In this study, GST fusion proteins containing the C-terminus of LMP1 were generated and used as substrates to survey the kinases that phosphorylate LMP1. Among several purified protein kinases tested, only protein kinase CK2 (CK2) could specifically phosphorylate LMP1. Using the in-gel kinase assay in the absence and presence of a selective CK2 inhibitor, 4,5,6,7-tetrabromobenzotriazole, CK2 was determined to be the major kinase to phosphorylate LMP1 in lymphoma and epithelial cell lines. This is the first study to show that CK2 is a potent kinase to phosphorylate LMP1 in vitro.

Serine 13 is the site of mitotic phosphorylation of human thymidine kinase

It has been reported that the polypeptide of thymidine kinase type 1 (TK1) from human and mouse cells can be modified by phosphorylation. Our laboratory has further shown that the level of human TK phosphorylation increases during mitotic arrest in different cell types (Chang, Z.-F., Huang, D.-Y., and Hsue, N.-C. (1994) J. Biol. Chem. 269:21249-21254). In the present study, we demonstrated that a mutation converting Ser13 to Ala abolished the mitotic phosphorylation of native TK1 expressed in Ltk- cells. Furthermore, we expressed recombinant proteins of wild-type and mutated human TK1 with fused FLAG epitope in HeLa cells, and confirmed the occurrence of mitotic phosphorylation on Ser13 of hTK1. By using an in vitro phosphorylation assay, it was shown that wild-type hTK1, but not mutant TK1(Ala13), could serve as a good substrate for Cdc2 or Cdk2 kinase. Coexpression of p21(waf1/cip1), which is a universal inhibitor of Cdk kinases, in Ltk- fibroblasts also suppressed mitotic phosphorylation of hTK1 expressed in this cell line. Thus, Cdc2 or related kinase(s) is probably involved in mitotic phosphorylation on Ser13 of the hTK1 polypeptide. We also found that mutation on Ser13 did not affect the functional activity of hTK1. As the sequences around Ser13 are highly conserved in vertebrate TK1s, we speculate that phosphorylation of Ser13 may play a role in the regulation of TK1 expression in the cell cycle.

Heparin and heparan sulfate bind to snake cardiotoxin. Sulfated oligosaccharides as a potential target for cardiotoxin action

Cardiotoxins (CTXs) from cobra venom show cytotoxicity toward several cell types. They cause systolic heart arrest and severe tissue necrosis. Their interaction with phospholipids is established but by itself fails to explain the specificity of these toxins; other component(s) of membrane must, therefore, intervene to direct them toward their target. We herein show, for the first time, that sulfated glycosaminoglycans, heparin, heparan sulfate (HS), chondroitin sulfate (CS), and dermatan sulfate (DS), interact with CTX A3, a major component of Taiwan cobra venom, by use of affinity chromatography, circular dichroism, absorbance, and fluorescence intensity and anisotropy measurements. The relative strength of binding, determined by the NaCl concentration required to dissociate the CTX-glycosaminoglycan complex, varied as follows: heparin > DS > CS > HS. In physiological buffer (8 mM Na2HPO4, 2.7 mM KCl, 1.8 mM KH2PO4, 138 mM NaCl, pH 7.4), however, only heparin and HS bound to CTX, with respective dissociation constants of 1.4 and 16 microM, while CS and DS failed to exhibit well defined binding behavior, as indicated by fluorescence measurements. We estimate that CTX makes 3-4 ionic contacts with heparin based on a salt-dependent binding study and that approximately 40% of binding free energy is derived from purely electrostatic interactions under physiological conditions. Sulfated pentasaccharide may be sufficient to bind to CTX. We also found that heparin accentuates the penetration of CTX into phospholipid membranes as analyzed by Langmuir monolayer measurement. In view of these results we propose that heparin-like moieties of the cell surface may modulate the action of CTX.

Expression of glutathione S-transferase-cardiotoxin fusion protein in Escherichia coli

We report here the construction of cardiotoxin V gene, from cobra snake venom (Naja naja atra), by chemically synthesized oligonucleotides and its expression as a glutathione S-transferase-cardiotoxin fusion protein in the inclusion bodies of Escherichia coli. The expression of cardiotoxin fusion protein in protein with a yield of about 35 mg/liter culture was confirmed by highly specific anti-peptide antibodies generated against the unique amino acid residues located at the tip of loop II of cardiotoxin V. Since the fusion protein can be easily treated by CNBr to free the toxin moiety, as revealed by immunoblotting of the cleaved protein, the results provide an avenue for future structural and functional studies of cardiotoxin molecules.

Hydrolysis of amyloid precursor protein-derived peptides by cysteine proteinases and extracts of rat brain clathrin-coated vesicles

Amyloid precursor proteins (APPs) and C-terminal fragments were colocalized with cysteine proteinase-like enzymes in purified rat brain clathrin-coated vesicles. Vesicular extracts degraded beta A4(12-28), yielding a product profile similar to that of purified rat brain cathepsin B. Cathepsin B degraded this peptide sequentially, with initial cleavage occurring at Val18-Phe19 and Phe19-Phe20 followed by release of dipeptides. Enzyme also hydrolyzed beta A4(1-40) at Phe19-Phe20 bond but at lower rates, likely due to aggregate formation. An octapeptide analogue of the domain adjacent to beta A4 (N-Ac-Val-Lys-Met-Asp-Ala-Glu-Phe-NH2) was also hydrolyzed by brain cathepsins B and L, and metalloendopeptidase 24.11. Enzymes acted at multiple sites, but only 24.11 cleaved the Met-Asp bond, thus resembling a proposed beta-secretase. Data imply that clathrin-coated vesicles contain cysteine-like proteinases capable of initiating the processing of APP or its fragments.

Freezing of phosphocholine headgroup in fully hydrated sphingomyelin bilayers and its effect on the dynamics of nonfreezable water at subzero temperatures

Differential scanning calorimetry (DSC) and nuclear magnetic resonance (NMR) spectroscopy are applied to characterize the nonfreezable water molecules in fully hydrated D2O/sphingomyelin at temperatures below 0 degrees C. Upon cooling, DSC thermogram displays two thermal transitions peaked at -11 and -34 degrees C. The high-temperature exothermic transition corresponds to the freezing of the bulk D2O, and the low-temperature transition, which has not previously been reported, can be ascribed to the freezing of the phosphocholine headgroup in the lipid bilayer. The dynamics of nonfreezable water are also studied by 2H NMR T1 (spin-lattice relaxation time) and T2e (spin-spin relaxation time obtained by two pulse echo) measurements at 30.7 MHz and at temperatures down to -110 degrees C. The temperature dependence of the T1 relaxation time is characterized by a distinct minimum value of 2.1 +/- 0.1 ms at -30 degrees C. T2e is discontinuous at temperature around -70 degrees C, indicating another freezing-like event for the bound water at this temperature. Analysis of the relaxation data suggest that nonfreezable water undergoes both fast and slow motions at characteristic NMR time scales. The slow motions are affected when the lipid headgroup freezes.

Mechanism of hemolysis of red blood cell mediated by ethanol

The effects of ethanol on hemolysis of human red blood cells (RBCs) were studied at 21 +/- 1 degrees C in the saline buffer (138 mM NaCl, 6.1 mM Na2HPO4, 1.4 mM NaH2PO4, 5 mM glucose and pH 7.4). The hemolysis process for ethanol-treated RBCs was preceded by the leakage of the small cation K+ from the cells indicating the colloid-osmotic nature of lysis. Since the extent of membrane lesion increased with an increasing ethanol concentration, osmotic protection experiments by using solutes varying in size were carried out to estimate the diameter of the pore. Quantitative analysis of the data by considering the effect of molecular seiving of the protectants with different sizes indicated that ethanol induced formation of membrane pores with a diameter of approximately 13 A. There was no detectable release of membrane fragments as assayed by the acetylcholinesterase activity, but the membrane structures were significantly perturbed, presumably at the membrane cytoskeletal protein, as evidenced by the altered rheological properties of RBC in the presence of ethanol. It is suggested that the creation of membrane pores might involve in the deranged cytoskeletal network of ethanol-treated RBC.

Biophysical correlates of lysophosphatidylcholine- and ethanol-mediated shape transformation and hemolysis of human erythrocytes. Membrane viscoelasticity and NMR measurement

The effects of monopalmitoylphosphatidylcholine (MPPC or lysophosphatidylcholine) and a series of short-chain primary alcohols (ethanol, 1-butanol and 1-hexanol) on cell shape, hemolysis, viscoelastic properties and membrane lipid packing of human red blood cells (RBCs) were studied. For MPPC, the effective membrane concentration to induce the formation of stage 3 echinocytes (8 x 10(6) molecules per cell) was one order of magnitude lower than that needed to induce 50% hemolysis (7 x 10(7) molecules per cell). In contrast, short-chain alcohols induced both shape changes and hemolysis within close concentration range (2.5 x 10(8) to 3.5 x 10(8) molecules per cell). Viscoelastic properties of the RBCs were studied by micropipette aspiration and correlated with shape change. Ethanol-treated RBCs showed a decrease in membrane elastic modulus and an increase in membrane viscosity in the recovery phase at the early stage of shape change. MPPC-treated cells showed the same type of viscoelastic changes, but these were not observed until the formation of stage 2 echinocytes. High-resolution solid-state 13C nuclear magnetic resonance technique was applied to study membrane lipid packing in the ghost membrane by following the chemical shift of hydrocarbon chains. Both MPPC and ethanol caused the 13C-NMR chemical shift to move upfield, indicating that membrane lipids were expanded due to the intercalation of these exogenous molecules. Using data obtained from model compounds, we convert values of chemical shift into a lipid packing parameter, i.e., number of gauche bonds for fatty acyl hydrocarbon chains. Approximately 10(8) interacting molecules per cell are required to induce a detectable change of lipid packing by both MPPC and ethanol. The results indicate that homolysis occurs at a smaller surface area for MPPC- than ethanol-treated RBCs. Our findings suggest that progressive changes in the molecular packing in the membrane lead eventually to hemolysis, but the mode responsible for shape transformation varies with these amphipaths.

Comparisons of lipid dynamics and packing in fully interdigitated monoarachidoylphosphatidylcholine and non-interdigitated dipalmitoylphosphatidylcholine bilayers: cross polarization/magic angle spinning 13C-NMR studies

13C-NMR spectra have been obtained at 50.3 MHz for monoarachidoylphosphatidylcholine (MAPC) and dipalmitoylphosphatidylcholine (DPPC) dispersions from 25 degrees C to 55 degrees C and for DPPC polycrystals at 25 degrees C using the cross polarization/magic angle spinning technique. Differential scanning calorimetric studies on DPPC and MAPC dispersions show comparable lipid phase transitions with transition temperatures at 41 degrees C and 45 degrees C, respectively, and thus enable the comparison of thermal, structural and dynamic differences between these two systems at corresponding temperatures. Conformational-dependent 13C chemical shift studies on DPPC dispersions demonstrate not only the coexistence of the tilted gel (L beta') and liquid-crystalline (L alpha) phases in the rippled gel (P beta') phase, but also the presence of an intermediate third microscopic phase as evidenced by three resolvable peaks for omega - 1 methylene carbon signals at the temperature interval between Tp and Tm. By comparing chemical shifts of MAPC in the hydrocarbon chain region with those of DPPC at similar reduced temperatures, it can be concluded that the packings are perturbed markedly in the middle segment of the fatty acyl chain during the lamellar to micellar transition. However, terminal methylene and methyl groups of interdigitated MAPC lamellae were found to be more ordered than those of non-interdigitated DPPC bilayers in the gel state. Interestingly, the terminal methyl groups of MAPC in the micelles remain to be relatively ordered; in fact, they are more ordered than the corresponding acyl chain end of DPPC in the liquid-crystalline state. Analysis of data obtained from rotating frame proton spin-lattice relaxation measurements shows a highly mobile phosphocholine headgroup, a rigid carbonyl group and an ordered hydrocarbon chain for lamellar MAPC in the interdigitated state. Furthermore, results suggest that free rotations of the glycerol C2-C3 bond within MAPC molecules may occur in the interdigitated bilayer, whereas intramolecular exchange between two conformations of the glycerol backbone in DPPC become possible at temperatures close to the pretransition temperature. Without isotope enrichment, we conclude that high-resolution solid-state 13C-NMR is indeed a useful technique which can be employed to study the packing and dynamics of phospholipids.

Effective bilayer expansion and erythrocyte shape change induced by monopalmitoyl phosphatidylcholine. Quantitative light microscopy and nuclear magnetic resonance spectroscopy measurements

When human erythrocytes are treated with exogenous monopalmitoyl phosphatidylcholine (MPPC), the normal biconcave disk shape red blood cells (RBC) become spiculate echinocytes. The present study examines the quantitative aspect of the relationship between effective bilayer expansion and erythrocyte shape change by a newly developed method. This method is based on the combination of direct surface area measurement of micropipette and relative bilayer expansion measurement of 13C crosspolarization/magic angle spinning nuclear magnetic resonance (NMR). Assuming that 13C NMR chemical shift of fatty acyl chain can be used as an indicator of lateral packing of membrane bilayers, it is possible for us to estimate the surface area expansion of red cell membrane induced by MPPC from that induced by ethanol. Partitions of lipid molecules into cell membrane were determined by studies of shape change potency as a function of MPPC and red cell concentration. It is found that 8(+/- 0.5) x 10(6) molecules of MPPC per cell will effectively induce stage three echinocytes and yield 3.2(+/- 0.2)% expansion of outer monolayer surface area. Surface area of normal cells determined by direct measurements from fixed geometry of red cells aspirated by micropipette was 118.7 +/- 8.5 microns2. The effective cross-sectional area of MPPC molecules in the cell membrane therefore was determined to be 48(+/- 4) A2, which is in agreement with those determined by x-ray from model membranes and crystals of lysophospholipids. We concluded that surface area expansion of RBC can be explained by a simple consideration of cross-sectional area of added molecules and that erythrocyte shape changes correspond quantitatively to the incorporated lipid molecules.

Diversity of rat brain cysteine proteinase inhibitors: isolation of low-molecular-weight cystatins and a higher-molecular weight T-kininogen-like glycoprotein

Conditions for extraction of rat brain soluble and particulate cysteine proteinase inhibitors (CPIs) were compared and an optimal one was selected to isolate low- and high-molecular-weight forms active toward papain or brain cathepsins B/L. The different forms were purified by affinity chromatography on alkylated papain, and identified on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels by use of Schiff's reagent, or by immunoblots using antisera to monomer or polymeric forms of human urinary cystatin c, to a human plasma histidine-rich glycoprotein (HRG), or to rat plasma T-kininogen. In particulates containing nuclei (P1) or synaptosomes (P2) the predominant CPI was an 80-kDa glycoprotein cross-reacting to anti-HRG and shown to be a T-kininogen by treatment with TPCK-trypsin, and subsequent bioassay of the released kinins. The levels found in rat brain were approximately 0.5 nmol/g wet weight. The higher-molecular-weight CPI potently inhibited cathepsin L hydrolysis of Leu-enkephalin at the Gly2-Gly3 bond with a Ki 10(-10) M. In contrast the low-molecular-weight CPIs were present in postmicrosomal fractions (S3) and cross-reacted with anti-cystatin c, but not with anti-HRG, anti-lysozyme, anti-beta protein amyloid peptide, or anti-T-kininogen. The low-molecular-weight forms were present at approximately 1-1.5 nmol/g wet weight and resembled "cerebrocystatin" purified previously from rat brain cytosol by M. Kopitar, F. Stern, and N. Marks [1983) Biochem. Biophys. Res. Commun. 112, 1000-1006.).