Neomycin reversibly disrupts mitotic progression in stamen hair cells of Tradescantia

Neomycin has been reported to inhibit polyphosphoinositide cycling by preventing the hydrolysis of phosphatidylinositol 4,5-bisphosphate into inositol 1,4,5-trisphosphate and 1,2-diacylglycerol. Inositol 1,4,5-trisphosphate, through the mobilization of calcium, and 1,2-diacylglycerol, through the activation of protein kinase C, trigger many physiological responses. The addition of 2 mM neomycin to stamen hair cells of Tradescantia virginiana at various points during mitosis arrests cells in prophase, prior to nuclear envelope breakdown, or in metaphase. Arrest in prophase is irreversible. Metaphase arrest can persist for over 2h before the cells attempt to revert to interphase without dividing. Entry into anaphase by the majority of cells in our sample arrested in metaphse occurred after treatment with 1,2-dioctanoylglycerol while 1,3-dioctanoylglycerol was totally ineffective at reversal. Perfusion of 100 /iM calcium chloride solution past the cells was sufficient to reverse arrest in approximately half of the cells in the sample. Magnesium could not be substituted for calcium in the reversal. Clindamycin, another member of this class of aminoglycoside antibiotics, with no known inhibitory effect on polyphosphoinositide cycling, is without effect on mitotic progression in stamen hair cells. Our results indirectly implicate one or more episodes of polyphosphoinositide cycling and its resultant protein phosphorylation by protein kinase C in the regulatory cascade that leads to anaphase.