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Query: UNIPROT:P01178 (oxytocin)
 15,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ruminant corpus luteum, in addition to producing progesterone, synthesizes and secretes oxytocin (OT) during the estrous cycle. Secretion of oxytocin occurs by exocytosis of membrane-encapsulated granules of this hormone. Exocytosis of oxytocin involves transport of granules through a cytoskeletal matrix including an actin cortex closely associated with the plasma membrane (PM). Actin filaments crosslinked by various proteins give rise to the structural integrity of the cortex. Myristoylated alanine-rich C kinase substrate (MARCKS), a protein specifically phosphorylated by protein kinase C (PKC), crosslinks actin filaments and anchors the actin network to the inner leaflet of the PM. There is evidence that the intact actin cortex may serve as a barrier, precluding fusion of transport vesicles with the PM. In some secretory cells, phosphorylation of MARCKS has resulted in its translocation from the PM to the cytoplasm with an associated disassembly of the actin cortex. Prostaglandin F(2alpha) (PGF(2alpha)) stimulation of the bovine corpus luteum during the midluteal phase of the estrous cycle activates PKC, which is associated with an increase in OT secretion in vivo and in vitro. Data are presented demonstrating that stimulation of bovine luteal cells with PGF(2alpha) on Day 8 of the cycle promotes rapid phosphorylation of MARCKS protein and causes its translocation from the PM to the cytoplasm and concomitant, enhanced exocytosis of OT. These data are consistent with the premise that MARCKS plays a role in the exocytotic process.
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PMID:Phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS) protein is associated with bovine luteal oxytocin exocytosis. 1085 36

Prostaglandin F2alpha (PGF2alpha)-induced secretion of oxytocin by the bovine corpus luteum involves the phosphorylation of a unique protein kinase C (PKC) substrate, myristoylated alanine-rich C kinase substrate (MARCKS) protein. This study was conducted to determine the specific PKC isoform engaged in phosphorylation of MARCKS protein in bovine luteal cells. In experiment 1, dispersed luteal cells recovered from the corpus luteum on d 8 of the estrous cycle were preincubated with [32P] orthophosphate and then exposed to PGF2alpha alone or in combination with PKC inhibitors. Autoradiography and densitometry of Western blots revealed that MARCKS protein was phosphorylated by a conventional PKC (cPKC) isoform. Experiment 2 was conducted to identify the specific cPKC isoform that phosphorylates MARCKS protein in luteal cells. Corpora lutea were removed from control and PGF2alpha-treated heifers on d 8 of the cycle, and PKC isoforms associated with membrane and cytosolic fractions were determined. Treatment with PGF2alpha increased membrane concentrations of PKCalpha within 5 min after treatment (p < 0.005). Collectively, these data suggest that phosphorylation of MARCKS protein coinciding with oxytocin secretion is mediated by PKCalpha.
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PMID:Prostaglandin F2alpha-activated protein kinase Calpha phosphorylates myristoylated alanine-rich C kinase substrate protein in bovine luteal cells. 1188 38

In the bovine corpus luteum (CL) phosphorylation of myristoylated alanine-rich C kinase substrate (MARCKS) protein in response to prostaglandin F2alpha (PGF2alpha) is correlated with the secretion of oxytocin. The present study was conducted to 1) examine the intracellular translocation characteristics of wild-type and mutant forms of a green fluorescent protein (GFP)-conjugated MARCKS (MARCKS-GFP) after PGF2alpha treatment and 2) evaluate PGF2alpha-induced temporal changes in MARCKS-GFP and actin cortex associated with exocytosis of oxytocin. In experiment 1, cells of the bovine CL were cultured on coverslips overnight. Then, wild-type and mutant MARCKS-GFP constructs were transfected separately into cells and expression was detected through fluorescence microscopy. Forty-eight hours after transfection, cells were treated with vehicle, PGF2alpha (56 nM), or a phorbol ester (12-O-tetradecanoylphorbol-13-acetate [TPA], 1 microM). Treatment of cells expressing wild-type MARCKS-GFP with PGF2alpha and TPA resulted in translocation of MARCKS from the plasma membrane to the cytoplasm within 2.5 min. Phosphorylation mutant MARCKS-GFP (m3) protein was localized on the plasma membrane, and treatments did not cause its translocation to the cytoplasm. Myristoylation mutant MARCKS-GFP (G2A) was observed solely in the cytoplasm, and no changes were detected in the intracellular location of this mutant MARCKS after treatment. In experiment 2, luteal cells were transfected with one of the three MARCKS-GFP constructs. Cells were then fixed and probed sequentially for oxytocin and filamentous actin. Results revealed that only wild-type MARCKS-GFP transfected large luteal cells contained advanced signs of exocytosis (peripheral movement of oxytocin vesicles; shorter actin filaments) with translocation of MARCKS-GFP from membrane to cytoplasm in response to PGF2alpha treatment. These data demonstrate that phosphorylation of membrane-bound MARCKS protein is requisite for exocytosis of oxytocin to occur in bovine large luteal cells.
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PMID:Spatiotemporal interactions of myristoylated alanine-rich C kinase substrate (MARCKS) protein with the actin cytoskeleton and exocytosis of oxytocin upon prostaglandin F2alpha stimulation of bovine luteal cells. 1293 Jul 25