Control of G2/M Transition in Xenopus by a Member of the p21-activated Kinase (PAK) Family: A Link Between Protein Kinase A and PAK Signaling Pathways?

Abstract

X-PAKs are involved in negative control of the process of oocyte maturation in Xenopus (1). In the present study, we define more precisely the events targetted by the kinase in the inhibition of the G 2 /M transition. We show that microinjection of recombinant X-PAK1-Cter active kinase into progesterone-treated oocytes prevents c-Mos accumulation and activation of both MAPK and maturation-promoting factor (MPF). In conditions permissive for MAPK activation, MPF activation still fails. We demonstrate that a constitutive truncated version of X-PAK1 (X-PAK1-Cter) does not prevent the association of cyclin B with p34 cdc2 but rather prevents the activation of the inactive complexes present in the oocyte. Proteins participating in the MPF amplification loop, including the Cdc25-activating Polo-like kinase are all blocked. Indeed, using active MPF, the amplification loop is not turned on in the presence of X-PAK1. Our results indicate that X-PAK and protein kinase A targets in the control of oocyte maturation are similar and furthermore that this negative regulation is not restricted to meiosis, because we demonstrate that G 2 /M progression is also prevented in Xenopus cycling extracts in the presence of active X-PAK1.

Functional interaction between c-Abl and the p21-activated protein kinase γ-PAK

“…The activity of a ␥-PAK homolog is high in frog oocytes and is decreased following fertilization and in early embryogenesis (15). A ␥-PAK homolog (X-PAK) has been implicated in the negative control of G 2 ͞M transition in Xenopus (16,17). Expression of wild-type ␥-PAK (␥-PAKwt) in mammalian cells, but not the kinase-inactive mutant K278R, inhibits cell division.…”

Phospho-Signaling at Oocyte Maturation and Fertilization: Set Up for Embryogenesis and Beyond Part I. Protein Kinases

“…On the other hand, catalytically active mutant of X-PAK is shown to suppress progesterone-induced Mos accumulation and MAPK activation. These data suggest that the endogenous PAK activity is involved in the cell cycle arrest before maturation (Faure et al 1997;Faure et al 1999). An inhibitory effect of X-PAK on oocyte maturation seems to be due to a PKA-like mechanism of suppression of the PLK-induced activation of Cdc25 phosphatase, which is a trigger of the activation of Cdc2/cyclin complex (i.e.…”

“…In mammals, maturing oocytes involves PKA phosphorylation of Cdc25B tyrosine phosphatase that leads to up-regulation of MPF activity. In marine worm, AMPK activity has been implicated in oocyte maturation, suggesting that intracellular balance of cAMP and AMP concentrations, as regulated by PDE and adenylate cyclase, is important for oocyte functions (Bornslaeger et al 1986;Browne et al 1990;Daar et al 1993;Faure et al 1998;Faure et al 1999;Grieco et al 1994;Grieco et al 1996;Matten et al 1994;Meijer et al 1989b;Newhall et al 2006;Pirino et al 2009;Nebreda 2002a, 2002b;Stricker and Smythe 2006;Stricker et al 2010b;Wang and Liu 2004;Webb et al 2008;Yu et al 2005;Zhang et al 2008). …”

“…An inhibitory effect of X-PAK on oocyte maturation seems to be due to a PKA-like mechanism of suppression of the PLK-induced activation of Cdc25 phosphatase, which is a trigger of the activation of Cdc2/cyclin complex (i.e. MPF) (Faure et al 1999). …”

Direct Binding and In Vivo Regulation of the Fission Yeast p21-Activated Kinase Shk1 by the SH3 Domain Protein Scd2

“…PAKs have diverse functions in eukaryotic organisms, including roles in regulation of cytoskeletal organization and cellular morphology (21,24,27,35), growth factor-induced signaling pathways (14,19,24,28,43), mitosis and meiosis (11,12,16,39), and apoptosis (31). PAKs are direct binding targets for the related p21 G proteins Cdc42 and Rac, but they do not bind to Rho, Ras, or other small G proteins (34).…”