Rho family small GTPase Rif regulates Wnt5a-Ror1-Dvl2 signaling and promotes lung adenocarcinoma progression.

Rho in filopodia (Rif), a member of the Rho family of small GTPases, induces filopodia formation primarily on the dorsal surface of cells; however, its function remains largely unclear. Here, we show that Rif interacts with Ror1, a receptor for Wnt5a that can also induce dorsal filopodia. Our immunohistochemical analysis revealed a high frequency of coexpression of Ror1 and Rif in lung adenocarcinoma. Lung adenocarcinoma cells cultured on Matrigel established front-rear polarity with massive filopodia on their front surfaces, where Ror1 and Rif were accumulated. Suppression of Ror1 or Rif expression inhibited cell proliferation, survival, and invasion, accompanied by the loss of filopodia and cell polarity in vitro, and prevented tumor growth in vivo. Furthermore, we found that Rif was required to activate Wnt5a-Ror1 signaling at the cell surface leading to phosphorylation of the Wnt signaling pathway hub protein Dvl2, which was further promoted by culturing the cells on Matrigel. Our findings reveal a novel function of Rif in mediating Wnt5a-Ror1-Dvl2 signaling, which is associated with the formation of polarized filopodia on 3D matrices in lung adenocarcinoma cells.

Brain-Derived Major Glycoproteins Are Possible Biomarkers for Altered Metabolism of Cerebrospinal Fluid in Neurological Diseases.

Cerebrospinal fluid (CSF) plays an important role in the homeostasis of the brain. We previously reported that CSF major glycoproteins are biosynthesized in the brain, i.e., lipocalin-type prostaglandin D2 synthase (L-PGDS) and transferrin isoforms carrying unique glycans. Although these glycoproteins are secreted from distinct cell types, their CSF levels have been found to be highly correlated with each other in cases of neurodegenerative disorders. The aim of this study was to examine these marker levels and their correlations in other neurological diseases, such as depression and schizophrenia, and disorders featuring abnormal CSF metabolism, including spontaneous intracranial hypotension (SIH) and idiopathic normal pressure hydrocephalus (iNPH). Brain-derived marker levels were found to be highly correlated with each other in the CSF of depression and schizophrenia patients. SIH is caused by CSF leakage, which is suspected to induce hypovolemia and a compensatory increase in CSF production. In SIH, the brain-derived markers were 2-3-fold higher than in other diseases, and, regardless of their diverse levels, they were found to be correlated with each other. Another abnormality of the CSF metabolism, iNPH, is possibly caused by the reduced absorption of CSF, which secondarily induces CSF accumulation in the ventricle; the excess CSF compresses the brain's parenchyma to induce dementia. One potential treatment is a "shunt operation" to bypass excess CSF from the ventricles to the peritoneal cavity, leading to the attenuation of dementia. After the shunt operation, marker levels began to increase within a week and then further increased by 2-2.5-fold at three, six, and twelve months post-operation, at which point symptoms had gradually attenuated. Notably, the marker levels were found to be correlated with each other in the post-operative period. In conclusion, the brain-derived major glycoprotein markers were highly correlated in the CSF of patients with different neurological diseases, and their correlations were maintained even after surgical intervention. These results suggest that brain-derived proteins could be biomarkers of CSF production.

Mesenchymal stem cell-derived CXCL16 promotes progression of gastric cancer cells by STAT3-mediated expression of Ror1.

Bone marrow-derived mesenchymal stem or stromal cells (MSC) have been shown to be recruited to various types of tumor tissues, where they interact with tumor cells to promote their proliferation, survival, invasion and metastasis, depending on the type of the tumor. We have previously shown that Ror2 receptor tyrosine kinase and its ligand, Wnt5a, are expressed in MSC, and Wnt5a-Ror2 signaling in MSC induces expression of CXCL16, which, in turn, promotes proliferation of co-cultured MKN45 gastric cancer cells via the CXCL16-CXCR6 axis. However, it remains unclear how CXCL16 regulates proliferation of MKN45 cells. Here, we show that knockdown of CXCL16 in MSC by siRNA suppresses not only proliferation but also migration of co-cultured MKN45 cells. We also show that MSC-derived CXCL16 or recombinant CXCL16 upregulates expression of Ror1 through activation of STAT3 in MKN45 cells, leading to promotion of proliferation and migration of MKN45 cells in vitro. Furthermore, co-injection of MSC with MKN45 cells in nude mice promoted tumor formation in a manner dependent on expression of Ror1 in MKN45 cells, and anti-CXCL16 neutralizing antibody suppressed tumor formation of MKN45 cells co-injected with MSC. These results suggest that CXCL16 produced through Ror2-mediated signaling in MSC within the tumor microenvironment acts on MKN45 cells in a paracrine manner to activate the CXCR6-STAT3 pathway, which, in turn, induces expression of Ror1 in MKN45 cells, thereby promoting tumor progression.

Spontaneous intracranial hypotension is diagnosed by a combination of lipocalin-type prostaglandin D synthase and brain-type transferrin in cerebrospinal fluid.

BACKGROUND: Spontaneous intracranial hypotension (SIH) is caused by cerebrospinal fluid (CSF) leakage. Definitive diagnosis can be difficult by clinical examinations and imaging studies. METHODS: SIH was diagnosed with the following criteria: (i) evidence of CSF leakage by cranial magnetic resonance imaging (MRI) findings of intracranial hypotension and/or low CSF opening pressure; (ii) no recent history of dural puncture. We quantified CSF proteins by ELISA or Western blotting. RESULTS: Comparing with non-SIH patients, SIH patients showed significant increase of brain-derived CSF glycoproteins such as lipocalin-type prostaglandin D synthase (L-PGDS), soluble protein fragments generated from amyloid precursor protein (sAPP) and "brain-type" transferrin (Tf). Serum-derived proteins such as albumin, immunoglobulin G, and serum Tf were also increased. A combination of L-PGDS and brain-type Tf differentiated SIH from non-SIH with sensitivity 94.7% and specificity 72.6%. CONCLUSION: L-PGDS and brain-type Tf can be biomarkers for diagnosing SIH. GENERAL SIGNIFICANCE: L-PGDS and brain-type Tf biosynthesized in the brain appears to be markers for abnormal metabolism of CSF.

Lectin-Based Assay for Glycoform-Specific Detection of α2,6-sialylated Transferrin and Carcinoembryonic Antigen in Tissue and Body Fluid.

Antibodies are useful for detecting glycoprotein antigens, but a conventional antibody recognizes only a protein epitope rather than a glycan. Thus, glycan isoform detection generally requires time- and labor-consuming processes such as lectin affinity column chromatography followed by sandwich ELISA. We recently found antigen-antibody reactions that were inhibited by lectin binding to glycans on the glycoprotein antigen, leading to a convenient glycoform-specific assay. Indeed, Sambucus sieboldiana agglutinin (SSA) lectin, a binder to sialylα2,6galactose residue, inhibited antibody binding to α2,6-sialylated transferrin (Tf) (SSA inhibition). SSA inhibition was not observed with other glycoforms, such as periodate-treated, sialidase-treated and sialidase/galactosidase-treated Tf, suggesting that the assay was glycoform-specific. SSA inhibition was also applicable for visualizing localization of α2,6-sialylated-Tf in a liver section. This is the first immunohistochemical demonstration of glycoform localization in a tissue section. SSA inhibition was utilized for establishing ELISA to quantify α2,6-sialylated carcinoembryonic antigen (CEA), a marker for various cancers. In addition, α2,6-sialylated-CEA was visualized in a colonic adenocarcinoma section by SSA inhibition. The method would further be applicable to a simple and rapid estimation of other α2,6-sialylated glycoproteins and have a potential aid to histopathological diagnosis.

A unique glycan-isoform of transferrin in cerebrospinal fluid: A potential diagnostic marker for neurological diseases.

BACKGROUND: Cerebrospinal fluid (CSF) is sequestered from blood by the blood-brain barrier and directly communicates with brain parenchymal interstitial fluid, leading to contain specific biomarkers of neurological diseases. SCOPE OF REVIEW: CSF contains glycan isoforms of transferrin (Tf): one appears to be derived from the brain and the other from blood. MAJOR CONCLUSIONS: CSF contains two glycan-isoforms; brain-type Tf and serum-type Tf. Glycan analysis and immunohistochemistry suggest that serum-type Tf having α2, 6sialylated glycans is derived from blood whereas brain-type Tf having GlcNAc-terminated glycans is derived from the choroid plexus, CSF producing tissue. The ratio of serum-type/brain-type Tf differentiates Alzheimer's disease from idiopathic normal pressure hydrocephalus, which is an elderly dementia caused by abnormal metabolism of CSF. The ratios in Parkinson's disease (PD) patients were higher than those of controls and did not appear to be normally distributed. Indeed, detrended normal Quantile-Quantile plot analysis reveals the presence of an independent subgroup showing higher ratios in PD patients. The subgroup of PD shows higher levels of CSF α-synuclein than the rest, indicating that PD includes two subgroups, which differ in levels of brain-type Tf and α-synuclein. GENERAL SIGNIFICANCE: Glycosylation in central nervous system appears to be unique. The unique glycan may be a tag for glycoprotein, which is biosynthesized in the central nervous system. This article is part of a Special Issue entitled Neuro-glycoscience, edited by Kenji Kadomatsu and Hiroshi Kitagawa.

Lectin inhibits antigen-antibody reaction in a glycoform-specific manner: Application for detecting α2,6sialylated-carcinoembryonic antigen.

Carcinoembryonic antigen (CEA) is a glycoprotein marker, which is widely used for diagnosing various cancers, especially colon adenocarcinoma. In addition, CEA mediates homotypic adhesion of colon adenocarcinoma cells, which appears to favor hematogenous metastasis. CEA carries α2,6sialyl residues on its N-glycans whereas a normal counterpart, normal fecal antigen-2, does α2,3sialyl residues, suggesting that cancer-specific  α2,6sialylation on CEA may play a role for cell invasion and metastasis. A simple and rapid estimation of α2,6sialyled CEA in detergent extracts from formalin-fixed colon adenocarcinoma by "lectin inhibition" is reported. In the lectin inhibition method, Sambucus sieboldiana Agglutinin (SSA) lectin, an α2,6sialic acid binder, was used as a glycoform-specific inhibitor for antigen-antibody reaction in ELISA. Detergent extracts from colon adenocarcinoma showed a fair amount of ELISA signal in the absence of SSA whereas the signal was markedly reduced (45≈74%) in the presence of SSA, suggesting that the extracts contains α2,6sialyled CEA. The presence of α2,6sialyled CEA in the extracts was confirmed by lectin microarray, in which SSA, Sambucus nigra agglutinin, and Trichosanthes japonica agglutinin I lectins were used as α2,6sialyl binders. Thus lectin inhibition is a simple and rapid method for detecting α2,6sialyled CEA even in crude detergent extracts from formalin-fixed adenocarcinoma tissue.

Correction: Hoshi et al. High Correlation among Brain-Derived Major Protein Levels in Cerebrospinal Fluid: Implication for Amyloid-Beta and Tau Protein Changes in Alzheimer's Disease. Metabolites 2022, 12, 355.

In the original publication [...].

Expression of Transferrin Protein and Messenger RNA in Neural Cells from Mouse and Human Brain Tissue.

Iron is an essential nutrient in the body. However, iron generates oxidative stress and hence needs to be bound to carrier proteins such as the glycoprotein transferrin (Tf) in body fluids. We previously reported that cerebrospinal fluid contains Tf glycan-isoforms that are derived from the brain, but their origins at the cellular level in the brain have not yet been elucidated. In the present report, we described the localization of Tf protein and mRNA in mouse and human brain tissue. In situ hybridization of mouse brain tissue revealed that Tf mRNA is expressed by different cell types such as epithelial cells in the choroid plexus, oligodendrocyte-like cells in the medulla, and neurons in the cortex, hippocampus, and basal ganglia. In contrast, Tf protein was barely detected by immunohistochemistry in hippocampal and some cortical neurons, but it was detected in other types of cells such as oligodendrocyte-like cells and choroid plexus epithelial cells. The results showed that Tf mRNA is expressed by neural cells, while Tf protein is expressed in different brain regions, though at very low levels in hippocampal neurons. Low Tf level in the hippocampus may increases susceptibility to iron-induced oxidative stress, and account for neuron death in neurodegenerative diseases.

High Correlation among Brain-Derived Major Protein Levels in Cerebrospinal Fluid: Implication for Amyloid-Beta and Tau Protein Changes in Alzheimer's Disease.

The cerebrospinal fluid (CSF) plays an important role in homeostasis of the brain. We previously demonstrated that major CSF proteins such as lipocalin-type prostaglandin D2 synthase (L-PGDS) and transferrin (Tf) that are biosynthesized in the brain could be biomarkers of altered CSF production. Here we report that the levels of these brain-derived CSF proteins correlated well with each other across various neurodegenerative diseases, including Alzheimer's disease (AD). In addition, protein levels tended to be increased in the CSF samples of AD patients compared with the other diseases. Patients at memory clinics were classified into three categories, consisting of AD (n = 61), mild cognitive impairment (MCI) (n = 42), and cognitively normal (CN) (n = 23), with MMSE scores of 20.4 ± 4.2, 26.9 ± 1.7, and 29.0 ± 1.6, respectively. In each category, CSF protein levels were highly correlated with each other. In CN subjects, increased CSF protein levels correlated well with those of AD markers, including amyloid-ß and tau protein, whereas in MCI and AD subjects, correlations declined with AD markers except p-tau. Future follow-up on each clinical subject may provide a clue that the CSF proteins would be AD-related biomarkers.

Total transferrin in cerebrospinal fluid is a novel biomarker for spontaneous intracranial hypotension.

Spontaneous intracranial hypotension (SIH) is caused by cerebrospinal fluid (CSF) leakage. Patients with SIH experience postural headaches, nausea, etc., due to CSF hypovolemia. Imaging studies and clinical examinations, such as radioisotope (RI) scintigraphy, are useful for diagnosing SIH. However, 20-30% of patients do not show typical morphology and clinical test results. We previously reported that CSF contains transferrin (Tf) isoforms:"brain-type" Tf derived from the choroid plexus and "serum-type" Tf derived from blood. We showed that both isoforms increased in the CSF of patients with SIH by Western blotting. In the present study, we demonstrate that conventional ELISA for quantifying total Tf is useful for diagnosing SIH more accurately than Western blotting. In addition, SIH with chronic subdural hematoma (CSDH) was also accurately diagnosed.　Total Tf in the CSF can serve as a useful biomarker for diagnosing SIH with or without CSDH.

Transferrin Biosynthesized in the Brain Is a Novel Biomarker for Alzheimer's Disease.

Glycosylation is a cell type-specific post-translational modification that can be used for biomarker identification in various diseases. Aim of this study is to explore glycan-biomarkers on transferrin (Tf) for Alzheimer's disease (AD) in cerebrospinal fluid (CSF). Glycan structures of CSF Tf were analyzed by ultra-performance liquid chromatography followed by mass spectrometry. We found that a unique mannosylated-glycan is carried by a Tf isoform in CSF (Man-Tf). The cerebral cortex contained Man-Tf as a major isofom, suggesting that CSF Man-Tf is, at least partly, derived from the cortex. Man-Tf levels were analyzed in CSF of patients with neurological diseases. Concentrations of Man-Tf were significantly increased in AD and mild cognitive impairment (MCI) comparing with other neurological diseases, and the levels correlated well with those of phosphorylated-tau (p-tau), a representative AD marker. Consistent with the observation, p-tau and Tf were co-expressed in hippocampal neurons of AD, leading to the notion that a combined p-tau and Man-Tf measure could be a biomarker for AD. Indeed, levels of p-tau x Man-Tf showed high diagnostic accuracy for MCI and AD; 84% sensitivities and 90% specificities for MCI and 94% sensitivities and 89% specificities for AD. Thus Man-Tf could be a new biomarker for AD.

Simple and Rapid Detection of Glycoforms by "Lectin Inhibition" Assay.

Glycoforms are otherwise identical proteins with different glycosylation. A lectin, Sambucus sieboldiana agglutinin (SSA), specifically binds glycoforms having α2,6-sialyl residues. The binding is found to inhibit antigen-antibody reaction; e.g., SSA inhibits anti-transferrin antibody binding to α2,6-sialylated transferrin (Tf) (SSA inhibition). SSA inhibition is not observed with other Tf glycoforms, indicating that the inhibition is glycoform-specific. Here we describe the application of SSA inhibition to ELISA as a specific assay for quantifying α2,6-sialylated Tf.

Glycoform-Specific Visualization in Immunohistochemistry by "Lectin Inhibition".

Antibodies are useful for localizing glycoprotein antigens in histochemistry, but they do not differentiate glycoforms in tissue sections because conventional antibodies recognize only protein epitopes rather than glycans. Glycan epitopes are recognized by lectins, which are found, occasionally, to inhibit antigen-antibody reaction in a glycoform-specific manner (lectin inhibition). Here we describe the application of lectin inhibition to immunohistochemistry for visualizing a glycoform in a tissue section.

Soluble protein tyrosine phosphatase receptor type Z (PTPRZ) in cerebrospinal fluid is a potential diagnostic marker for glioma.

BACKGROUND: High-grade glioma is the most pervasive and lethal of all brain malignancies. Despite advances in imaging technologies, discriminating between gliomas and other brain diseases such as multiple sclerosis (MS) often requires brain biopsy. Several reports show that protein tyrosine phosphatase receptor Z (PTPRZ) is highly expressed in glioblastoma, and we found that a soluble cleaved form of PTPRZ (sPTPRZ) was present in the cerebrospinal fluid (CSF). The aim of this study was to determine whether the sPTPRZ level in CSF has utility as a diagnostic marker for glioma. METHODS: Microarray datasets from normal brain tissue and brain tumors were obtained from the Gene Expression Omnibus. PTPRZ protein expression in clinical specimens was evaluated by immunohistochemistry. Semiquantitative western blotting was used to measure sPTPRZ levels in CSF samples from patients with glioma, schwannoma, MS, or nontumor disorders. RESULTS: Expression of PTPRZ mRNA and protein was markedly increased in glioblastoma, astrocytoma, oligodendroglioma, and schwannoma tissues compared with control brain tissue. sPTPRZ was present at significantly elevated levels in the CSF of patients with glioma (grades 1-4), but not in patients with schwannoma or MS, compared with the control samples. Receiver operating characteristic curve analysis showed that sPTPRZ in CSF could discriminate between glioma and MS patients (area under the curve 0.9676; P < .0001). CONCLUSIONS: sPTPRZ in CSF is a promising diagnostic biomarker for glioma and could reduce the need for a surgical biopsy.

Ratio of Alpha 2-Macroglobulin Levels in Cerebrospinal Fluid and Serum: An Expression of Neuroinflammation in Acute Disseminated Encephalomyelitis.

BACKGROUND: Acute encephalitis and encephalopathy are life-threatening diseases in children. However, no laboratory examinations are performed for their early diagnosis and treatment. Alpha 2-macroglobulin (α2M) is a blood glycoprotein that increases during the early stages of inflammation. In the present study, we investigated the role of α2M levels in acute encephalitis and encephalopathy. METHODS: We analyzed the cerebrospinal fluid and serum samples from patients with acute disseminated encephalomyelitis, infection-related acute encephalopathy, febrile status epilepticus, and febrile seizure simplex type. Samples were collected from the pediatric department of hospitals throughout the Fukushima Prefecture between January 1, 1999, and May 31, 2012. RESULTS: α2M levels in the cerebrospinal fluid were 4.7 (3.8-8.4) µg/mL for acute disseminated encephalomyelitis, 2.1 (1.1-2.3) µg/mL for infection-related acute encephalopathy, 1.1 (0.9-6.4) µg/mL for febrile status epilepticus, and 1.0 (0.8-1.1) µg/mL for febrile seizure simplex type. α2M levels in patients with acute disseminated encephalomyelitis were significantly higher than those in patients with infection-related acute encephalopathy and febrile seizure simplex type (P = 0.019 and P = 0.002, respectively). The ratio of α2M level in the cerebrospinal fluid to that in the serum in patients with acute disseminated encephalomyelitis was significantly higher than the ratio in patients with febrile status epilepticus (P = 0.04). In patients with acute disseminated encephalomyelitis, α2M levels in the cerebrospinal fluid decreased with treatment. CONCLUSIONS: Our results suggest that α2M levels in the cerebrospinal fluid reflect the neuroinflammatory status of patients with acute disseminated encephalomyelitis.

Rapid increase of 'brain-type' transferrin in cerebrospinal fluid after shunt surgery for idiopathic normal pressure hydrocephalus: a prognosis marker for cognitive recovery.

Idiopathic normal pressure hydrocephalus (iNPH) is a dementia-inducing disorder. Primary cause of iNPH is speculated to be a reduction of cerebrospinal fluid (CSF) absorption, which secondarily induces hydrocephalus, compression of brain, and reduction of CSF production. Patients are treated by surgically inserting a shunt to deliver excess CSF to the abdominal cavity. The prognosis for cognitive improvement after shunt surgery has been difficult to predict. We therefore investigated various CSF proteins, hoping to find a biomarker predictive of cognitive performance one to two years after shunt surgery. CSF proteins of 34 iNPH and 15 non-iNPH patients were analysed by Western blotting, revealing two glycan isoforms of transferrin (Tf); 'brain-type' Tf with N-acetylglucosaminylated glycans and 'serum-type' Tf with α2, 6-sialylated glycans. Brain-type Tf levels decreased in iNPH but rapidly returned to normal levels within 1-3 months after shunt surgery. This change was positively correlated with recovery from dementia, per Mini-Mental State Examination and Frontal Assessment Battery scores at 11.8 ± 7.7 months post-operation, suggesting that brain-type Tf is a prognostic marker for recovery from dementia after shunt surgery for iNPH. Histochemical staining with anti-Tf antibody and an N-acetylglucosamine-binding lectin suggests that brain-type Tf is secreted from choroid plexus, CSF-producing tissue.

Evaluation of blood-brain barrier function by quotient alpha2 macroglobulin and its relationship with interleukin-6 and complement component 3 levels in neuropsychiatric systemic lupus erythematosus.

Although quotient of alpha2 macroglobulin (Qα2MG) was previously reported to be useful for the evaluation of blood-brain barrier (BBB) function, it is not commonly used. We therefore evaluated BBB function among the various subsets of neuropsychiatric systemic lupus erythematosus (NPSLE) using quotient Q α2MG. Furthermore, we determined the correlation between Q α2MG and cerebrospinal (CSF) interleukin (IL)-6 level and quotient complement component 3 (Q C3). To determine intrathecal production of C3, the C3 index (Q C3/Q α2MG) was also calculated. Fifty-six patients with SLE were included in this study. Of these, 48 were diagnosed with NPSLE, consisting of 30 diffuse NPSLE patients (acute confusional state (ACS): n = 14, non-ACS: n = 16) and 18 patients with focal NPSLE. CSF IL-6 concentration, and paired serum and CSF levels of α2MG and C3, were measured by enzyme-linked immuno solvent assay (ELISA). The Q α2MG, Q C3, and C3 index were then calculated. Q α2MG, Q C3, and IL-6 concentrations in the CSF were significantly elevated in NPSLE compared with non-NPSLE. Among the subsets of NPSLE, significant increases in Q α2MG, CSF IL-6, and Q C3 were observed in ACS compared with non-ACS or focal NPSLE. There was a positive correlation between CSF IL-6 level and Q α2MG, as well as between Q C3 and Q α2MG, in diffuse NPSLE. There were no significant differences in C3 index between NPSLE and non-NPSLE, as well as among the subgroups of NPSLE. Our study suggests that BBB disruption is present in ACS, and elevated levels of IL-6 and C3 in CSF in diffuse NPSLE, especially in ACS, might result from their entry to the CSF from the systemic circulation through the damaged BBB, as well as increased intrathecal production. Furthermore, Q α2MG might be useful for the evaluation of BBB integrity.

Subgroup differences in 'brain-type' transferrin and α-synuclein in Parkinson's disease and multiple system atrophy.

Two transferrin (Tf) glycan-isoforms were previously found in cerebrospinal fluid (CSF); one appears to be derived from serum (Tf-2) and the other from choroid plexus, a CSF-producing tissue (Tf-1). To analyse metabolic differences associated with the two isoforms, their ratio (Tf-2/Tf-1) was defined as the Tf index. Here we report that Tf indices of patients with tauopathies including Alzheimer's disease (2.29 + 0.64) were similar to those of neurological controls (2.07 + 0.87) (P = 0.147). In contrast, Tf indices with Parkinson's disease (PD, 3.38 ± 1.87) and multiple system atrophy (MSA, 3.15 ± 1.72) were higher than those of the controls (2.07 ± 0.87), the P-values being < 0.001 and 0.024, respectively. Tf indices of PD and MSA did not appear to be normally distributed. Indeed, detrended normal Quantile-Quantile plot analysis revealed the presence of an independent subgroup showing higher Tf indices in PD and MSA. The subgroup of PD showed higher levels of CSF α-synuclein (38.3 ± 17.8 ng/ml) than the rest (25.3 ± 11.3 ng/ml, P = 0.012). These results suggest that PD (and MSA) includes two subgroups, which show different metabolism of CSF transferrin and α-synuclein.

In situ visualization of a glycoform of transferrin: localization of α2,6-sialylated transferrin in the liver.

We previously found that a lectin, Sambucus sieboldiana agglutinin (SSA), bound to α2,6-sialylated glycan epitopes on transferrin and inhibited anti-transferrin antibody binding to the antigen in ELISA (SSA inhibition). Here we report that SSA inhibition is applicable to immunohistochemistry, localizing α2,6-sialylated transferrin in the liver. Immunohistochemistry using anti-transferrin polyclonal antibody revealed that transferrin was detected in hepatocytes near interlobular veins. Addition of SSA lectin markedly attenuated the staining. Sialidase treatment of a liver section abolished SSA binding and concomitantly cancelled SSA inhibition, suggesting that SSA binding to glycan epitopes on the section was essential for the inhibition. To examine the importance of proximity between antigen epitopes and SSA-binding (glycosylation) sites, we prepared two anti-peptide antibodies against partial amino acid sequences of transferrin. One antibody (Tf-596Ab) is against a peptide sequence, Cys596-Ala614, which is proximal to N-glycosylation sites (Asn-432 and Asn-630). The other (Tf-120Ab) is against a peptide sequence, Val120-Cys137, distal to the sites. The staining signals of Tf-596Ab were reduced by the addition of SSA, whereas those of Tf-120Ab were reduced only a little. This result suggests that proximity of the antigen epitope to SSA binding sites is critical for SSA inhibition in immunohistochemistry.