Development of polyclonal antibodies and evaluation of a sensitive radioimmunoassay for detection and measurement of synaptophysin

Malignant cell-derived extracellular vesicles express different chromogranin epitopes compared to prostasomes

BACKGROUND

Prostasomes are nanosized extracellular vesicles exocytosed by prostate epithelial cells. They have been assigned many roles propitious to sperm in favor of fertilization. Prostatic cancer cells can also produce and secrete extracellular vesicles.

METHODS

We assessed using ELISA, the surface expression of chromogranin proproteins on prostasomes and malignant extracellular vesicles of four different prostate cancer cell-lines, two hormone sensitive and two hormone refractory. We used a panel of chromogranin A and chromogranin B antibodies against peptides in-between hypothetical cleavage sites along the proproteins.

RESULTS

A diverging pattern of chromogranin peptides was apparent when comparing prostasomes and malignant extracellular vesicles indicating a phenotypical change. We also compared western blot patterns (prostasomes and malignant extracellular vesicles) for selected antibodies that displayed high absorbances in the ELISA. Western blot analyses revealed various cleavage patterns of those proproteins that were analyzed in prostasomes and extracellular vesicles.

CONCLUSION

Chromogranins are constituents of not only prostasomes but also of malignant prostate cell-derived extracellular vesicles with different amino acid sequences exposed at the membrane surface giving rise to a mosaic pattern. These findings may be of relevance for designing new assays for detection or even possible treatment of prostate cancers.

Cellular expression and specific intragranular localization of chromogranin A, chromogranin B, and synaptophysin during ontogeny of pancreatic islet cells: an ultrastructural study

INTRODUCTION AND AIMS

To get more insight into the differentiation patterns of pancreatic islet neuroendocrine cells and granules during ontogeny, the expression and localization of chromogranin A (CgA), chromogranin B (CgB), synaptophysin, and insulin were ultrastructurally studied with the immunogold technique in porcine and human pancreatic islet neuroendocrine cells.

METHODOLOGY AND RESULTS

In porcine pancreas at early fetal stage, CgA was visualized throughout the immature granules in all neuroendocrine cells. Later, CgB also was expressed with the same pattern in most granules in all types of cells. In neonatal islets, CgA was localized in the periphery of immature alpha- and beta-cell granules and throughout the matrix of delta-cell granules; CgB was distributed throughout the matrix of these granules. In adult islets, alpha-cell granules stored CgA in the halo and CgB in both the core and the halo, beta-cell granules stored both CgA and CgB in their cores, and in delta-cell granules, both substances were mixed throughout the matrix. In all ontogenetic stages, synaptophysin was demonstrated in all cell types and granules. Insulin was expressed in early fetal cells of both pigs and humans, and colocalization with CgA, CgB, and synaptophysin was demonstrated.

CONCLUSION

The early expression of CgA and synaptophysin may reflect a role at early fetal stages, and the individual localization of CgA and CgB upon differentiation indicates individual functions.

Characteristics of human prostasomes isolated from three different sources

BACKGROUND

Prostasomes are organelles secreted by human prostate epithelial cells and appear freely in semen. Most prostasomal functional and biochemical characteristics have been settled on basis of seminal prostasomes (SP).

METHODS

Three types of prostasomes, viz., from seminal plasma, prostate gland (native), and prostate cancer bone metastasis, were isolated and compared for their biochemical and functional characteristics.

RESULTS

Flow cytometry showed that all three types of prostasomes had a similar size distribution and electrophoresis revealed close similarities in banding pattern. Also, a high cholesterol/phospholipid ratio and some marker enzymes were distinctive common features. The unusual chromogranin B (CgB)/chromogranin A (CgA) ratio with CgB in abundance over CgA, previously found only in SP, was also valid for the native (NP) and metastasis-derived prostasomes (MP). The latter prostasome type contained a 10-fold higher amount of CgA compared to the others. SP and MP showed the same promotive effect on sperm forward motility, whereas NP did not. All three prostasome types exhibited an antibacterial activity against Bacillus megaterium.

CONCLUSIONS

Since the three prostasome types were isolated from different environments, our data support the view that the common characteristics were prostasome-genuine.

Reduction of the small synaptic vesicle protein synaptophysin but not the large dense core chromogranins in the left thalamus of subjects with schizophrenia

BACKGROUND

It has been hypothesized that a lesion in the neuronal circuits of thalamus might contribute to the symptoms in schizophrenia. It has also been suggested that impaired synaptic transmission is an important component of the pathophysiology of schizophrenia. In the present study we assess the synaptic integrity of thalamus by means of examining the protein levels of: (1) synaptophysin, a membrane bound protein of small synaptic vesicles, and (2) chromogranins, a family of soluble secretory proteins stored and released from the secretory large dense-core vesicles.

METHODS

The brains of 9 patients with schizophrenia and 9 age-matched control subjects were studied. The levels of synaptophysin and chromogranins were measured by radioimmunoassays.

RESULTS

The amount of synaptophysin in the left thalamus was significantly decreased (p = .036) in the schizophrenic group (2655 +/- 605 nmol synaptophysin/mg total protein) compared to the control group (3248 +/- 827 nmol synaptophysin/mg total protein). There were no differences between the groups in the levels of chromogranins, nor in the levels of synaptophysin of the right thalamus.

CONCLUSIONS

These findings indicate defect synaptic function in the left thalamus of patients with schizophrenia. This may be the cause of a reduction of synaptic terminals or a defect limited to certain structures of the synapse, namely the small presynaptic vesicles.

Expression of p68 protein kinase and its prognostic significance during IFN-alpha therapy in patients with carcinoid tumours

The aim of this study was to evaluate the antiproliferative effects of interferon alpha (IFN-alpha) on neuroendocrine differentiated cell lines and, retrospectively, to assess the prognostic significance of p68 protein kinase (PKR) induction in neuroendocrine gut and pancreatic tumour patients. Archive specimens from 56 patients were studied, 43 before IFN-alpha and 56 during therapy. The tissues were immunostained for p68 protein kinase (PKR) using the monoclonal antibody (MAb) TJ4C4. A significant increase in immunostaining after treatment with IFN-alpha compared with before treatment (3.47 +/- 0.12 versus 2.72 +/- 0.15, P < 0.001) was noted. The p68 score was significantly increased after treatment only in patients with stable disease before = 2.71 +/- 0.19, after = 3.40 +/- 0.14 (P < 0.001) or an objective response before 3.13 +/- 0.22, after = 4.00 +/- 0.24 (P < 0.05) but not in those with progressive disease (before = 2.32 +/- 0.24, after 2.86 +/- 0.26, NS). A low p68 score (< 3.0) during treatment was a predictor of shorter duration of response and overall survival (P = 0.0062 and P < 0.0001, respectively). Furthermore, IFN-alpha showed a significant antiproliferative effect (by [3H]thymidine incorporation) on two carcinoid tumour cell lines in a dose-dependent manner which correlated with a dose-dependent induction of p68 mRNA and protein expression (by Northern and Western blot analysis). We conclude that IFN-alpha can effectively inhibit the in vitro growth of carcinoid tumor cell lines and upregulates the expression of p68 at both mRNA and protein levels in carcinoid tumours. The induction of p68 could be a prognostic indicator of response in patients with carcinoid tumours during IFN-alpha treatment.

Determination of synapsin I and synaptophysin in body fluids by two-site enzyme-linked immunosorbent assays

Two-site enzyme-linked immunosorbent assays (ELISA) have been established for the specific and sensitive determination of two membrane proteins of the small synaptic vesicles (SSV), namely: peripheral synapsin I and integral synaptophysin. The ELISA used highly specific capture monoclonal antibodies (mAB) and polyclonal antibodies (pAB) as detectors. For synapsin I, the mAB were newly generated, whereas for synaptophysin, the commercially available mAB SY38 was applied. In order to calibrate the ELISA and to raise pAB, both proteins were purified in the mg-range. Synapsin I was purified by conventional means from human and porcine brain and synaptophysin was purified by immunoaffinity chromatography from porcine brain. Using the ELISA, neither synapsin I nor synaptophysin could be determined in serum or cerebrospinal fluid (CSF) from healthy donors or patients suffering various neurological disorders or pheochromocytomas. For this reason, the degradation of both proteins in serum and CSF was investigated. With the exception of synaptophysin measured in serum, both proteins exhibited fast rates of degradation. Despite the negative results in human body fluids, the two ELISA are appropriate for the quantification of these membrane proteins in neuronal or neuroendocrine cell extracts or preparations of SSV.

Prostasomes are neuroendocrine-like vesicles in human semen

BACKGROUND

Prostasomes are prostate-derived organelles that exist extracellularly in human seminal plasma.

METHODS

In this study, we have investigated and characterized human prostasomes with regard to their contents of synaptophysin, members of the chromogranin family, and some neuropeptides.

RESULTS

By radioimmunoassay measurement and electron microscopy we show the presence of the neuroendocrine markers chromogranin B, neuropeptide Y, and vasoactive intestinal polypeptide in about equimolar amount in human prostasomes and chromogranin A in about 2% of that amount. To our knowledge, such a high ratio of chromogranin B to chromogranin A has never before been observed. The membrane-bound protein synaptophysin, a well-established immunocytochemical marker for neuroendocrine cells and neurones, was also detected. Hence, we show that synaptophysin could be used as a marker for intact prostasomes.

CONCLUSIONS

The presence of synaptophysin has recently been shown in the serotonincontaining vesicles in platelets. A protein with a similar structure denoted granulophysin has been found in granulocytes and prostasomes. It is suggested that synaptophysin and granulophysin molecules are members of a family of proteins, maybe expressed in all cells that have regulated release of granule content. Our presented data indicate a neurotransmittor function of the prostasomes. The target cells are however not known but could be either the spermatozoa, the epithelial mucous cells of the uterus or tubas or perhaps the ovum.

A novel enzyme-linked immunosorbent assay for determination of synaptophysin as compared with other quantification procedures

A two-sided enzyme-linked immunosorbent assay (ELISA) has been established for reliable, specific and sensitive determination of synaptophysin (SYN), an intrinsic membrane protein of the small synaptic vesicles. This ELISA used a highly specific monoclonal antibody (SY 38) as capture reagent and a specific SYN antiserum in combination with a secondary peroxidase-conjugated antibody for detection. Calibration was carried out with immunoaffinity-purified SYN from porcine cortex. The sensitivity was found to be improved substantially when the ELISA was compared with previously used dot-immunobinding assays. This ELISA allowed rapid and reliable determination of SYN from detergent lysed homogenates, partially and highly purified preparations of rat, porcine and human brain. SYN was determined in highly purified small synaptic vesicles, and it was calculated to be 5.8% of total detergent solubilized protein.