Characterization of the "giant precursors" (70-80K) of vasopressin and oxytocin in the rat hypothalamus

Provasopressin expression by breast cancer cells: implications for growth and novel treatment strategies

The arginine vasopressin (AVP) gene is expressed in certain cancers such as breast cancer, where it is believed to act as an autocrine growth factor. However, little is known about the regulation of the AVP protein precursor (proAVP) or AVP-mediated signaling in breast cancer and this study was undertaken to address some of the basic issues. The cultured cell lines examined (Mcf7, Skbr3, BT474, ZR75, Mcf10a) and human breast cancer tissue extract were found to express proAVP mRNA. Western analysis revealed multiple forms of proAVP protein were present in cell lysates, corresponding to those detected in human hypothalamus extracts. Monoclonal antibodies directed against different regions of proAVP bound to intact live Mcf7 and Skbr3 cells. Dexamethasone increased the amount of proAVP-associated glycopeptide (VAG) secreted by Skbr3 cells and a combination of dexamethasone, IBMX and 8br-cAMP increased cellular levels of VAG. Exogenous AVP (1, 10, and 100 nM) elevated phospho-ERK1/2 levels, and increased cell proliferation was observed in the presence of 10 nM AVP. Concurrent treatment with the V1a receptor antagonist SR49059 reduced the effects of AVP on proliferation in Mcf7 cells, and abolished it in Skbr3 cells. Results here show that proAVP components are found at the surface of Skbr3 and Mcf7 cells and are also secreted from these cells. In addition, they show that AVP promotes cancer cell growth, apparently through a V1-type receptor-mediated pathway and subsequent ERK1/2 activation. Thus, strategies for targeting proAVP should be examined for their effectiveness in diagnosing and treating breast cancer.

Monoclonal antibodies identify two novel proteins associated with vasopressin secretory granules of the rat neurohypophysis

Immunocytochemical and immunoblotting technique have been used to characterize the antigens recognized by two monoclonal antibodies (MAbs C6 and D5) produced against dissociated cells from punches of neonatal supraoptic (SON) and paraventricular (PVN) hypothalamic nuclei of the rat. Peroxidase immunocytochemistry revealed that both MAbs label magnocellular perikarya in the adult and neonatal SON and PVN as well as smaller neurons in the suprachiasmatic nucleus. Axons of the hypothalamo-neurohypophysial tract are also immunolabeled within the hypothalamus and zona interna of the median eminence, and C6 and D5 each bind specifically to both the adult and neonatal neurohypophysis. Dual-label immunofluorescence experiments employing C6 or D5 simultaneously with rabbit antisera specific for either oxytocin, neurophysin or vasopressin neurophysin revealed that C6 binds only to vasopressinergic magnocellular perikarya in the SON, while D5 labels both vasopressinergic and a small subset of oxytocinergic magnocellular neurons. Post-embedding immunogold analysis of MAb binding to the neurohypophysis at the ultrastructural level showed that both C6 and D5 recognize antigens associated with large dense core neurosecretory granules in a subset of neurosecretory axons. Initial biochemical characterization of the antigens recognized by C6 and D5 was performed using SDS-PAGE and Western immunoblotting. MAbs C6 and D5 label single protein bands with apparent molecular weights of 38 and 68 kDa, resp., in blots of reduced extracts from the adult neurointermediate lobe. No cross-reactivity between C6 and D5 and the neurophysins was apparent, nor did anti-neurophysin sera recognize the bands identified by C6 and D5. We have therefore designated these novel antigens as VPGP38 and VPGP68 for VasoPressin Granule Proteins.