scholarly journals Sperm-induced calcium oscillations at fertilisation in ascidians are controlled by cyclin B1-dependent kinase activity

Development ◽  
2000 ◽  
Vol 127 (3) ◽  
pp. 631-641 ◽  
Author(s):  
M. Levasseur ◽  
A. McDougall
Keyword(s):  
Kinase Activity ◽  
Cyclin B1 ◽  
Calcium Oscillations ◽  
Full Length ◽  
Cyclin Dependent Kinase ◽  
Early Embryos ◽  
Protein Map ◽  
M Phase ◽  
Mitogen Activated Protein ◽  
Cell Cycle Machinery

The generation of calcium oscillations at fertilisation and during mitosis appears to be controlled by the cell cycle machinery. For example, the calcium oscillations in oocytes and embryos occur during metaphase and terminate upon entry into interphase. Here we report the manipulation of sperm-triggered calcium oscillations by cyclin-dependent kinase (CDK) activity, the major component of maturation/M phase promoting factor (MPF). To control the CDK activity we microinjected mRNAs encoding full-length GFP-tagged cyclin B1 or a truncated and therefore stabilised form of cyclin B1 ((delta)90) into unfertilised oocytes. In the presence of full-length cyclin B1, the calcium oscillations terminate when cyclin B1 levels fall along with the concomitant fall in the associated CDK activity. In addition, when the CDK activity is elevated indefinitely with (delta)90 cyclin B1, the calcium oscillations also continue indefinitely. Finally, in oocytes that contain low mitogen-activated protein (MAP) kinase activity and elevated CDK activity, the sperm-triggered calcium oscillations are again prolonged. We conclude that the CDK activity of the ascidian oocyte can be regarded as a positive regulator of sperm-triggered calcium oscillations, a finding that may apply to other oocytes that display sperm-triggered calcium oscillations at fertilisation. Furthermore, these findings may have a bearing upon the mitotic calcium signals of early embryos.

Biochemical characterization of mitogen-activated protein (MAP) kinase activity in Toxoplasma gondii

2000 ◽  
Vol 86 (7) ◽  
pp. 588-598 ◽  
Author(s):  
Marie-Paule Roisin ◽  
Florence Robert-Gangneux ◽  
Claudine Creuzet ◽  
Jean Dupouy-Camet
Keyword(s):  
Toxoplasma Gondii ◽  
Map Kinase ◽  
Kinase Activity ◽  
Biochemical Characterization ◽  
Protein Map ◽  
Mitogen Activated Protein

Mitogen-activated protein kinase in human eggs

Zygote ◽  
1999 ◽  
Vol 7 (2) ◽  
pp. 181-185 ◽  
Author(s):  
Qing-Yuan Sun ◽  
Zeev Blumenfeld ◽  
Sara Rubinstein ◽  
Shlomit Goldman ◽  
Yael Gonen ◽  
...  
Keyword(s):  
Map Kinase ◽  
Mammalian Species ◽  
Germinal Vesicle ◽  
Mitogen Activated Protein Kinase ◽  
Early Embryos ◽  
Protein Map ◽  
Mitogen Activated Protein ◽  
Kinase Phosphorylation ◽  
Cycle Regulation ◽  
Kinase Expression

Mitogen-activated protein (MAP) kinase in human eggs has been investigated by using immunoblotting with both anti-Active MAPK and anti-ERK2 antibodies. The results showed that the main form of MAP kinase was p42ERK2. It was in a dephosphorylated form in oocytes at the germinal vesicle stage, but fully phosphorylated in unfertilised mature eggs. MAP kinase phosphorylation was significantly decreased when pronuclei were formed after intracytoplasmic sperm injection. Neither MAP kinase expression nor activity was detected in morphologically degenerated eggs. Although MAP kinase still existed in early embryos arrested at the 8-cell or morula stages, little, if any, activity could be detected. These data suggest that MAP kinase may play an important role in the cell cycle regulation of human eggs, as in other mammalian species.

MITOGEN-ACTIVATED PROTEIN (MAP) KINASE ACTIVITY INCREASES AFTER FOCAL CEREBRAL ISCHEMIA IN RATS

1998 ◽  
Vol 26 (Supplement) ◽  
pp. 84A
Author(s):  
John W. Kuluz ◽  
Charles L. Schleien ◽  
Y. Kang ◽  
Joseph Neary
Keyword(s):  
Cerebral Ischemia ◽  
Map Kinase ◽  
Kinase Activity ◽  
Focal Cerebral Ischemia ◽  
Protein Map ◽  
Mitogen Activated Protein

scholarly journals Ssp2 Binding Activates the Smk1 Mitogen-Activated Protein Kinase

2017 ◽  
Vol 37 (10) ◽  
Author(s):  
Chong Wai Tio ◽  
Gregory Omerza ◽  
Timothy Phillips ◽  
Hua Jane Lou ◽  
Benjamin E. Turk ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Chromosome Segregation ◽  
Kinase Activity ◽  
Specific Protein ◽  
Mitogen Activated Protein Kinase ◽  
Activation Loop ◽  
Cyclin Dependent Kinase ◽  
Content Type ◽  
Dual Specificity ◽  
Mitogen Activated Protein

ABSTRACT Smk1 is a meiosis-specific mitogen-activated protein kinase (MAPK) in Saccharomyces cerevisiae that couples spore morphogenesis to the completion of chromosome segregation. Similar to other MAPKs, Smk1 is controlled by phosphorylation of a threonine (T) and a tyrosine (Y) in its activation loop. However, it is not activated by a dual-specificity MAPK kinase. Instead, T207 in Smk1's activation loop is phosphorylated by the cyclin-dependent kinase (CDK)-activating kinase (Cak1), and Y209 is autophosphorylated in an intramolecular reaction that requires the meiosis-specific protein Ssp2. In this study, we show that Smk1 is catalytically inert unless it is bound by Ssp2. While Ssp2 binding activates Smk1 by a mechanism that is independent of activation loop phosphorylation, binding also triggers autophosphorylation of Y209 in Smk1, which, along with Cak1-mediated phosphorylation of T207, further activates the kinase. Autophosphorylation of Smk1 on Y209 also appears to modify the specificity of the MAPK by suppressing Y kinase and enhancing S/T kinase activity. We also found that the phosphoconsensus motif preference of Ssp2/Smk1 is more extensive than that of other characterized MAPKs. This study therefore defines a novel mechanism of MAPK activation requiring binding of an activator and also shows that MAPKs can be diversified to recognize unique phosphorylation motifs.

scholarly journals Mitotic Effects of a Constitutively Active Mutant of the Xenopus Polo-Like Kinase Plx1

1999 ◽  
Vol 19 (12) ◽  
pp. 8625-8632 ◽  
Author(s):  
Yue-Wei Qian ◽  
Eleanor Erikson ◽  
James L. Maller
Keyword(s):  
Xenopus Laevis ◽  
Aspartic Acid ◽  
Kinase Activity ◽  
Spindle Assembly ◽  
Cyclin B ◽  
Interphase Nuclei ◽  
Aspartic Acid Residue ◽  
Early Embryos ◽  
M Phase ◽  
Egg Extracts

ABSTRACT During mitosis the Xenopus polo-like kinase 1 (Plx1) plays key roles in the activation of Cdc25C, in spindle assembly, and in cyclin B degradation. Previous work has shown that the activation of Plx1 requires phosphorylation on serine and threonine residues. In the present work, we demonstrate that replacement of Ser-128 or Thr-201 with a negatively charged aspartic acid residue (S128D or T201D) elevates Plx1 activity severalfold and that replacement of both Ser-128 and Thr-201 with Asp residues (S128D/T201D) increases Plx1 activity approximately 40-fold. Microinjection of mRNA encoding S128D/T201D Plx1 into Xenopus oocytes induced directly the activation of both Cdc25C and cyclin B-Cdc2. In egg extracts T201D Plx1 delayed the timing of deactivation of Cdc25C during exit from M phase and accelerated Cdc25C activation during entry into M phase. This supports the concept that Plx1 is a “trigger” kinase for the activation of Cdc25C during the G2/M transition. In addition, during anaphase T201D Plx1 reduced preferentially the degradation of cyclin B2 and delayed the reduction in Cdc2 histone H1 kinase activity. In early embryos S128D/T201D Plx1 resulted in arrest of cleavage and formation of multiple interphase nuclei. Consistent with these results, Plx1 was found to be localized on centrosomes at prophase, on spindles at metaphase, and at the midbody during cytokinesis. These results demonstrate that in Xenopus laevis activation of Plx1 is sufficient for the activation of Cdc25C at the initiation of mitosis and that inactivation of Plx1 is required for complete degradation of cyclin B2 after anaphase and completion of cytokinesis.

scholarly journals Activation of the Xenopus cyclin degradation machinery by full-length cyclin A

1996 ◽  
Vol 109 (5) ◽  
pp. 1071-1079 ◽  
Author(s):  
C. Jones ◽  
C. Smythe
Keyword(s):  
Protein Synthesis ◽  
Dna Replication ◽  
Kinase Activity ◽  
Cyclin A ◽  
Cell Types ◽  
Cyclin B1 ◽  
Full Length ◽  
Cyclin B ◽  
Cdc2 Kinase ◽  
Nuclear Envelope Breakdown

The entry into mitosis is dependent on the activation of mitotic forms of cdc2 kinase. In many cell types, cyclin A-associated kinase activity peaks just prior to that of cyclin B, although the precise role of cyclin A-associated kinase in the entry into mitosis is still unclear. Previous work has suggested that while cyclin B is capable of triggering cyclin destruction in Xenopus cell-free systems, cyclin A-associated kinase is not able to support this function. Here we have expressed a full-length human cyclin A in Escherichia coli and purified the protein to homogeneity by virtue of an N-terminal histidine tag. We have found that when added to Xenopus cell-free extracts free of cyclin B and incapable of protein synthesis, the temporal pattern of cyclin A-associated cdc2 kinase activity showed distinct differences that were dependent on the concentration of cyclin A added. When cyclin A was added to a concentration that generated levels of cdc2 kinase activity capable of inducing nuclear envelope breakdown, the histone H1 kinase activity profile was bi-phasic, consisting of an activation phase followed by an inactivation phase. Inactivation was found to be due to cyclin destruction, which was prevented by mos protein. Cyclin destruction was followed by nuclear reassembly and an additional round of DNA replication, indicating that there is no protein synthesis requirement for DNA replication in this embryonic system. It has been suggested that the evolutionary recruitment of cyclin A into an S phase function may have necessitated the loss of an original mitotic ability to activate the cyclin destruction pathway. The results presented here indicate that cyclin A has not lost the ability to activate its own destruction and that cyclin A-mediated activation of the cyclin destruction pathway permitted destruction of cyclin B1 as well as cyclin A, indicating that there are not distinct cyclin A and cyclin B destruction pathways. Thus the ordered progression of the cell cycle requires the careful titration of cyclin. A concentration in order to avoid activation of the cyclin destruction pathway before sufficient active cyclin B/cdc2 kinase has accumulated.

Lysophosphatidylcholine activates mesangial cell PKC and MAP kinase by PLCγ-1 and tyrosine kinase-Ras pathways

1999 ◽  
Vol 277 (3) ◽  
pp. F328-F337 ◽  
Author(s):  
Babu V. Bassa ◽  
Daeyoung D. Roh ◽  
Nosratola D. Vaziri ◽  
Michael A. Kirschenbaum ◽  
Vaijinath S. Kamanna
Keyword(s):  
Tyrosine Kinase ◽  
Map Kinase ◽  
Protein Tyrosine Kinase ◽  
Kinase Activity ◽  
Mesangial Cells ◽  
Kinase Activation ◽  
Kinase C ◽  
Protein Map ◽  
Mitogen Activated Protein ◽  
Pkc Activation

Although lysophosphatidylcholine (LPC)-mediated cellular responses are attributed to the activation of protein kinase C (PKC), relatively little is known about the upstream signaling mechanisms that regulate the activation of PKC and downstream mitogen-activated protein (MAP) kinase. LPC activated p42 MAP kinase and PKC in mesangial cells. LPC-mediated MAP kinase activation was inhibited (but not completely) by PKC inhibition, suggesting additional signaling events. LPC stimulated protein tyrosine kinase (PTK) activity and induced Ras-GTP binding. LPC-induced MAP kinase activity was blocked by the PTK inhibitor genistein. Because LPC increased PTK activity, we examined the involvement of phospholipase Cγ-1 (PLCγ-1) as a key participant in LPC-induced PKC activation. LPC stimulated the phosphorylation of PLCγ-1. PTK inhibitors suppressed LPC-induced PKC activity, whereas the same had no effect on phorbol 12-myristate 13-acetate-mediated PKC activity. Other lysophospholipids [e.g., lysophosphatidylinositol and lysophosphatidic acid (LPA)] also induced MAP kinase activity, and only LPA-induced MAP kinase activation was sensitive to pertussis toxin. These results indicate that LPC-mediated PKC activation may be regulated by PTK-dependent activation of PLCγ-1, and both PKC and PTK-Ras pathways are involved in LPC-mediated downstream MAP kinase activation.

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