Vitellogenesis in Oncopeltus fasciatus: PLC/IP(3), DAG/PK-C pathway triggered by CaM.
In Oncopeltus fasciatus, evidence shown here indicates it is calmodulin (CaM) that activates phospholipase-C (PLC), beginning a signalling pathway necessary for endocytic uptake of yolk precursor molecules. Epithelial cell-produced CaM, transported to oocytes via gap junctions, has been shown to be required for receptor-mediated endocytic uptake of vitellogenins (Vgs, the protein precursors of yolk). To determine if CaM was directly or indirectly stimulating the phospholipase-C (PLC) signalling cascade and thus controlling Vg endocytosis we used a series of molecules known to inactivate various elements of the pathway. W-7 prevents CaM from interacting with other molecules. Neomycin isolates PIP(2) from PLC. U-73122 directly inactivates PLC. 2-APB blocks IP(3) receptors which would otherwise cause release of Ca(2+). Verapamil and CdCl(2) block Ca(2+) release channels. Staurosporin and calphostin are inhibitors of PK-C. 1-Hexadecyl-2-acetyl glycerol (HAG) binds to diacylglycerol (DAG). Through the use of these antagonists we show here that: (1) the activation of phospholipase-C in this system requires CaM. (2) Stimulated phospholipase-C converts PIP(2) into IP(3) and DAG. (3) IP(3) causes increase in cytosolic Ca(2+). (4) DAG and Ca(2+) each stimulate phosphokinase-C, resulting in endocytosis of Vgs.
Brown
Patrick T
PT
Department of Biology, West Chester University, West Chester, PA 19383, USA.
Herbert
Paul
P
Woodruff
Richard I
RI
D000818:Animals; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004075:Diglycerides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology*; D004963:Estrenes / Q000494:pharmacology; D020062:Heteroptera / Q000502:physiology*; D008856:Microscopy, Fluorescence; D009281:Naphthalenes / Q000494:pharmacology; D009355:Neomycin / Q000494:pharmacology; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011760:Pyrrolidinones / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D019311:Staurosporine / Q000494:pharmacology; D013449:Sulfonamides / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014818:Vitellogenesis / Q000502:physiology*
C538758:2-aminoethyl diphenylborinate; D001896:Boron Compounds; D002147:Calmodulin; D004075:Diglycerides; D004963:Estrenes; D009281:Naphthalenes; D011760:Pyrrolidinones; D013449:Sulfonamides; C061465:calphostin complex; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C017967:W 7; D017853:Phosphotransferases (Alcohol Group Acceptor); C051038:Inositol 1,4,5-trisphosphate 3-kinase; D011493:Protein Kinase C; D010738:Type C Phospholipases; D019311:Staurosporine; D009355:Neomycin; D002118:Calcium