Phospholipase C and myosin light chain kinase inhibition define a common step in actin regulation during cytokinesis
✍ Scribed by Raymond Wong; Lacramioara Fabian; Arthur Forer; Julie A Brill
- Book ID
- 104492572
- Publisher
- BioMed Central
- Year
- 2007
- Tongue
- English
- Weight
- 920 KB
- Volume
- 8
- Category
- Article
- ISSN
- 1471-2121
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✦ Synopsis
Abstract
Background
Phosphatidylinositol 4,5-bisphosphate (PIP~2~) is required for successful completion of cytokinesis. In addition, both PIP~2~ and phosphoinositide-specific phospholipase C (PLC) have been localized to the cleavage furrow of dividing mammalian cells. PLC hydrolyzes PIP~2~ to yield diacylglycerol (DAG) and inositol trisphosphate (IP~3~), which in turn induces calcium (Ca^2+)^ release from the ER. Several studies suggest PIP~2~ must be hydrolyzed continuously for continued cleavage furrow ingression. The majority of these studies employ the N-substituted maleimide U73122 as an inhibitor of PLC. However, the specificity of U73122 is unclear, as its active group closely resembles the non-specific alkylating agent N-ethylmaleimide (NEM). In addition, the pathway by which PIP~2~ regulates cytokinesis remains to be elucidated.
Results
Here we compared the effects of U73122 and the structurally unrelated PLC inhibitor ET-18-OCH~3~ (edelfosine) on cytokinesis in crane-fly and Drosophila spermatocytes. Our data show that the effects of U73122 are indeed via PLC because U73122 and ET-18-OCH~3~ produced similar effects on cell morphology and actin cytoskeleton organization that were distinct from those caused by NEM. Furthermore, treatment with the myosin light chain kinase (MLCK) inhibitor ML-7 caused cleavage furrow regression and loss of both F-actin and phosphorylated myosin regulatory light chain from the contractile ring in a manner similar to treatment with U73122 and ET-18-OCH~3~.
Conclusion
We have used multiple inhibitors to examine the roles of PLC and MLCK, a predicted downstream target of PLC regulation, in cytokinesis. Our results are consistent with a model in which PIP~2~ hydrolysis acts via Ca^2+^ to activate myosin via MLCK and thereby control actin dynamics during constriction of the contractile ring.