Effect of inhibition of the catalytic activity of cyclic amp‐dependent protein kinase on mitosis in PtK₁ cells

Abstract

Evidence has suggested that cyclic AMP, acting through activation of the type II cyclic AMP-dependent protein kinase, may play a role in the regulation of interphase and mitotic microtubules. In order to examine the potential role of the type II cAMP-dependent kinase during mitosis, dividing PtK1 cells were microinjected with two specific inhibitors of the catalytic activity of the type II kinase. These inhibitors were a specific protein inhibitor of cAMP-dependent protein kinase (PKI) and an affinity-purified polyclonal antiserum (anti-C) directed against the catalytic subunit of the kinase. Both have been shown previously to inhibit kinase activity in vitro. Microinjection of PKI during early- to mid-prophase significantly delayed the progression of the cells through mitosis, with the greatest delay occurring in metaphase. PKI injected during prometaphase also delayed progression through mitosis but to a lesser extent. Microinjection of anti-C during early- to mid-prophase also caused a significant delay in the completion of mitosis, with many cells becoming "hung up" in prometaphase. Anti-C injected during prometaphase had little effect on subsequent progression through mitosis. Microinjection of either anti-C or PKI during metaphase had no discernible effect. No effect on anaphase movement of chromosomes was observed with any treatment. These results provide further evidence that cAMP-dependent phosphorylation may be involved in the regulation of mitosis, although whether it acts directly through regulation of mitotic spindle microtubules is unclear.

1,2‐dioctanoylglycerol accelerates or retards mitotlc progression in Tradescantia stamen hair cells as a function of the time of its addition

“…Some of these proteins are probably phosphorylated specifically before or during mitosis while others are present throughout the cell cycle, becoming organized in physiologically provocative patterns in and around the mitotic apparatus [Davis et al, 1983;Vandre et al, 1984;Millar et al, 1987;Kuriyama, 1989;Vandre and Borisy, 19891. The common characteristic shared by these polypeptides is that they become phosphorylated and dephosphorylated during specific stages of mitosis, probably by temporally specific kinase and phosphatase activities [Davis et al, 1983;Vandre et al, 1984;Browne et al, 1987;Millar et al, 1987;Wordeman and Cande, 1987;Kuriyama, 1989;Vandre and Borisy, 19891. Specific kinases appear to be involved in the phosphorylation of lamins, for the breakdown of the nuclear envelope [Gerace and Blobel, 1980;Suprynowicz and Gerace, 19861 and during late metaphase for the phosphorylation of specific spindle polypeptides [Dinsmore and Sloboda, 19881.…”

Patterns of cyclic AMP‐dependent protein kinase gene expression during ontogeny of the murine palate

“…Steady state levels of both RIIa and RIIp mRNAs were greatest during the early stages of palate development when tissue growth is most pronounced. PKA can directly and specifically affect cell growth (Browne et al, 1987) and the proliferative potential of embryonic palatal cells is regulated in part by cAMP (Pisano et al, 1986). Thus, the RII regulatory subunits of PKA may be involved in regulating cell proliferation in the embryonic palate.…”