Evidence for cell surface and internal phospholipase activity in ascidian eggs
Article first published online: 27 OCT 2003
Development, Growth & Differentiation
Volume 39, Issue 5, pages 655–660, October 1997
How to Cite
Goode, C. A., Gamboa-Pinto, A. J., Cruz, R., Gough, L. L., Lund, C. V. and Lambert, C. C. (1997), Evidence for cell surface and internal phospholipase activity in ascidian eggs. Development, Growth & Differentiation, 39: 655–660. doi: 10.1046/j.1440-169X.1997.t01-4-00013.x
- Issue published online: 27 OCT 2003
- Article first published online: 27 OCT 2003
- Received 29 October 1996; revised 2 June 1997; accepted 3 June 1997.
- Ascidia ceratodes;
Upon fertilization, ascidian eggs release a cell surface glycosidase used in the block to polyspermy and undergo cortical contractions resulting from increased intracellular calcium levels. The glycosidase is released by fertilization, calcium ionophores or added phospholipase C (PLC) activity. The PLC inhibitor D609 blocks glycosidase release. Intact Ascidia ceratodes eggs cleave 4-methylumbelliferyl-phospho-choline when it is added to seawater. This yields highly fluorescent 4-methylumbelliferone. Authentic phospholipase C but not phospholipase D can cleave this substrate. Thus, the authors believe that cleavage of the substrate is specific for PLC activity. Eggs incubated in the fluorogenic substrate after having been washed and detergent extracted were not fluorescent. Therefore the substrate failed to enter intact cells. Glycosidase release and PLC activity were stimulated by ionomycin. Octylglucoside or Triton X-100 extracts of ascidian eggs had two forms of phospholipase activity as shown by ion affinity chromatography: PL1 eluting at 0.25 mol/L NaCl and PL2 eluting at 0.6mol/L NaCl. The PL1 appeared to be isolated as a single protein. When surface proteins were labeled with non-penetrating biotin and were subsequently reacted with streptavidin, half of the PLC activity bound. This demonstrates that half the ascidian egg PLC activity is located on the surface of either the egg or follicle cell, and half is located within the egg.