scholarly journals MuSK Kinase Activity is Modulated By A Serine Phosphorylation Site in The Kinase Loop

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
B. Z. Camurdanoglu ◽  
C. Hrovat ◽  
G. Dürnberger ◽  
M. Madalinski ◽  
K. Mechtler ◽  
...  
Keyword(s):  
Neuromuscular Junction ◽  
Cluster Size ◽  
Kinase Activity ◽  
Phosphorylation Site ◽  
Serine Phosphorylation ◽  
Activation Loop ◽  
Achr Cluster ◽  
Kinase Activation ◽  
Muscle Specific Kinase ◽  
Postsynaptic Differentiation

Abstract The neuromuscular junction (NMJ) forms when a motor neuron contacts a muscle fibre. A reciprocal exchange of signals initiates a cascade of signalling events that result in pre- and postsynaptic differentiation. At the centre of these signalling events stands muscle specific kinase (MuSK). MuSK activation, kinase activity and subsequent downstream signalling are crucial for NMJ formation as well as maintenance. Therefore MuSK kinase activity is tightly regulated to ensure proper NMJ development. We have identified a novel serine phosphorylation site at position 751 in MuSK that is increasingly phosphorylated upon agrin stimulation. S751 is also phosphorylated in muscle tissue and its phosphorylation depends on MuSK kinase activity. A phosphomimetic mutant of S751 increases MuSK kinase activity in response to non-saturating agrin concentrations . In addition, basal MuSK and AChR phosphorylation as well as AChR cluster size are increased. We believe that the phosphorylation of S751 provides a novel mechanism to relief the autoinhibition of the MuSK activation loop. Such a lower autoinhibition could foster or stabilize MuSK kinase activation, especially during stages when no or low level of agrin are present. Phosphorylation of S751 might therefore represent a novel mechanism to modulate MuSK kinase activity during prepatterning or NMJ maintenance.

scholarly journals Two Distinct Phosphorylation Pathways Have Additive Effects on Abl Family Kinase Activation

2003 ◽  
Vol 23 (11) ◽  
pp. 3884-3896 ◽  
Author(s):  
Keith Q. Tanis ◽  
Darren Veach ◽  
Henry S. Duewel ◽  
William G. Bornmann ◽  
Anthony J. Koleske
Keyword(s):  
Tyrosine Kinases ◽  
Kinase Activity ◽  
Intramolecular Interactions ◽  
Activation Loop ◽  
Additive Effects ◽  
Nonreceptor Tyrosine Kinase ◽  
Kinase Activation ◽  
Surface Receptors ◽  
Nonreceptor Tyrosine Kinases ◽  
Stimulation Of

ABSTRACT The activities of the related Abl and Arg nonreceptor tyrosine kinases are kept under tight control in cells, but exposure to several different stimuli results in a two- to fivefold stimulation of kinase activity. Following the breakdown of inhibitory intramolecular interactions, Abl activation requires phosphorylation on several tyrosine residues, including a tyrosine in its activation loop. These activating phosphorylations have been proposed to occur either through autophosphorylation by Abl in trans or through phosphorylation of Abl by the Src nonreceptor tyrosine kinase. We show here that these two pathways mediate phosphorylation at distinct sites in Abl and Arg and have additive effects on Abl and Arg kinase activation. Abl and Arg autophosphorylate at several sites outside the activation loop, leading to 5.2- and 6.2-fold increases in kinase activity, respectively. We also find that the Src family kinase Hck phosphorylates the Abl and Arg activation loops, leading to an additional twofold stimulation of kinase activity. The autoactivation pathway may allow Abl family kinases to integrate or amplify cues relayed by Src family kinases from cell surface receptors.

scholarly journals A phosphorylation of RIPK3 kinase initiates an intracellular apoptotic pathway that promotes corpus luteum regression

2021 ◽  
Author(s):  
Dianrong Li ◽  
Jie Chen ◽  
Jia Guo ◽  
Lin Li ◽  
Gaihong Cai ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Granulosa Cells ◽  
Kinase Activity ◽  
Caspase 8 ◽  
Activation Loop ◽  
Spontaneous Apoptosis ◽  
Apoptotic Pathway ◽  
Apoptosis Pathway ◽  
Luteal Regression ◽  
Kinase Activation

AbstractReceptor-interacting serine/threonine-protein kinase 3 (RIPK3) normally signals to necroptosis by phosphorylating MLKL. We report here that when the cellular RIPK3 chaperone Hsp90/CDC37 level is low, RIPK3 also signals to apoptosis. The apoptotic function of RIPK3 requires phosphorylation of the serine 165/threonine 166 sites on its kinase activation loop, resulting in inactivation of RIPK3 kinase activity while gaining the ability to recruit RIPK1, FADD, and caspase-8 to form a cytosolic caspase-activating complex, thereby triggering apoptosis. We found that PGF2α induces RIPK3 expression in luteal granulosa cells in the ovary to cause luteal regression through this RIPK3-mediated apoptosis pathway. Mice carrying homozygous phosphorylation-resistant RIPK3 S165A/T166A knockin mutations failed to respond to PGF2α but retained pro-necroptotic function, whereas mice with phospho-mimicking S165D/T166E homozygous knockin mutation underwent spontaneous apoptosis in multiple RIPK3-expressing tissues and died shortly after birth. Thus, RIPK3 signals to either necroptosis or apoptosis depending on its serine 165/threonine 166 phosphorylation status.

scholarly journals Kinase Function of Brassinosteroid Receptor Specified by Two Allosterically Regulated Subdomains

2022 ◽  
Vol 12 ◽  
Author(s):  
Khawar Ali ◽  
Wenjuan Li ◽  
Yaopeng Qin ◽  
Shanshan Wang ◽  
Lijie Feng ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Kinase Activity ◽  
The Other ◽  
Activation Loop ◽  
Biological Functions ◽  
Kinase Activation ◽  
Downstream Signaling ◽  
Signaling Function ◽  
Insight Into

Plants acquire the ability to adapt to the environment using transmembrane receptor-like kinases (RLKs) to sense the challenges from their surroundings and respond appropriately. RLKs perceive a variety of ligands through their variable extracellular domains (ECDs) that activate the highly conserved intracellular kinase domains (KDs) to control distinct biological functions through a well-developed downstream signaling cascade. A new study has emerged that brassinosteroid-insensitive 1 (BRI1) family and excess microsporocytes 1 (EMS1) but not GASSHO1 (GSO1) and other RLKs control distinct biological functions through the same signaling pathway, raising a question how the signaling pathway represented by BRI1 is specified. Here, we confirm that BRI1-KD is not functionally replaceable by GSO1-KD since the chimeric BRI1-GSO1 cannot rescue bri1 mutants. We then identify two subdomains S1 and S2. BRI1 with its S1 and S2 substituted by that of GSO1 cannot rescue bri1 mutants. Conversely, chimeric BRI1-GSO1 with its S1 and S2 substituted by that of BRI1 can rescue bri1 mutants, suggesting that S1 and S2 are the sufficient requirements to specify the signaling function of BRI1. Consequently, all the other subdomains in the KD of BRI1 are functionally replaceable by that of GSO1 although the in vitro kinase activities vary after replacements, suggesting their functional robustness and mutational plasticity with diverse kinase activity. Interestingly, S1 contains αC-β4 loop as an allosteric hotspot and S2 includes kinase activation loop, proposedly regulating kinase activities. Further analysis reveals that this specific function requires β4 and β5 in addition to αC-β4 loop in S1. We, therefore, suggest that BRI1 specifies its kinase function through an allosteric regulation of these two subdomains to control its distinct biological functions, providing a new insight into the kinase evolution.

scholarly journals Raf-1 forms a stable complex with Mek1 and activates Mek1 by serine phosphorylation

1993 ◽  
Vol 90 (23) ◽  
pp. 10947-10951 ◽  
Author(s):  
W Huang ◽  
A Alessandrini ◽  
C M Crews ◽  
R L Erikson
Keyword(s):  
Kinase Activity ◽  
Polyclonal Antibodies ◽  
Phosphorylation Site ◽  
Serine Phosphorylation ◽  
Stable Complex ◽  
Sf9 Cells ◽  
Tight Association

Recombinant Mek1 and Raf-1 proteins produced in Sf9 cells undergo a tight association both in vivo and in vitro, which apparently does not depend on additional factors or the kinase activity of Mek1 or Raf-1. The complex can be disrupted by two polyclonal antibodies raised against Raf-1 peptides. Coinfection with Raf-1 activates Mek1 > 150-fold, and coinfection with Raf-1 and Mek1 activates Erk1 approximately 90-fold. The activation of Mek1 by Raf-1 involves only serine phosphorylation, which is directly proportional to the extent of Mek1 activation. Phosphopeptide maps suggest a single Raf-1 phosphorylation site on mek1.

scholarly journals Erratum: Corrigendum: MuSK Kinase Activity is Modulated By A Serine Phosphorylation Site in The Kinase Loop

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
B. Z. Camurdanoglu ◽  
C. Hrovat ◽  
G. Dürnberger ◽  
M. Madalinski ◽  
K. Mechtler ◽  
...  
Keyword(s):  
Kinase Activity ◽  
Phosphorylation Site ◽  
Serine Phosphorylation

scholarly journals mTORC2 controls the activity of PKC and Akt by phosphorylating a conserved TOR interaction motif

2021 ◽  
Vol 14 (678) ◽  
pp. eabe4509
Author(s):  
Timothy R. Baffi ◽  
Gema Lordén ◽  
Jacob M. Wozniak ◽  
Andreas Feichtner ◽  
Wayland Yeung ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Kinase Activity ◽  
Phosphorylation Site ◽  
Activation Loop ◽  
Dimer Interface ◽  
Agc Kinases ◽  
Evolutionarily Conserved ◽  
Phosphorylation Event ◽  
Hydrophobic Motif

The complex mTORC2 is accepted to be the kinase that controls the phosphorylation of the hydrophobic motif, a key regulatory switch for AGC kinases, although whether mTOR directly phosphorylates this motif remains controversial. Here, we identified an mTOR-mediated phosphorylation site that we termed the TOR interaction motif (TIM; F-x3-F-pT), which controls the phosphorylation of the hydrophobic motif of PKC and Akt and the activity of these kinases. The TIM is invariant in mTORC2-dependent AGC kinases, is evolutionarily conserved, and coevolved with mTORC2 components. Mutation of this motif in Akt1 and PKCβII abolished cellular kinase activity by impairing activation loop and hydrophobic motif phosphorylation. mTORC2 directly phosphorylated the PKC TIM in vitro, and this phosphorylation event was detected in mouse brain. Overexpression of PDK1 in mTORC2-deficient cells rescued hydrophobic motif phosphorylation of PKC and Akt by a mechanism dependent on their intrinsic catalytic activity, revealing that mTORC2 facilitates the PDK1 phosphorylation step, which, in turn, enables autophosphorylation. Structural analysis revealed that PKC homodimerization is driven by a TIM-containing helix, and biophysical proximity assays showed that newly synthesized, unphosphorylated PKC dimerizes in cells. Furthermore, disruption of the dimer interface by stapled peptides promoted hydrophobic motif phosphorylation. Our data support a model in which mTORC2 relieves nascent PKC dimerization through TIM phosphorylation, recruiting PDK1 to phosphorylate the activation loop and triggering intramolecular hydrophobic motif autophosphorylation. Identification of TIM phosphorylation and its role in the regulation of PKC provides the basis for AGC kinase regulation by mTORC2.

scholarly journals A phosphorylation of RIPK3 kinase initiates an intracellular apoptotic pathway that promotes prostaglandin2α-induced corpus luteum regression

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Dianrong Li ◽  
Jie Chen ◽  
Jia Guo ◽  
Lin Li ◽  
Gaihong Cai ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Granulosa Cells ◽  
Kinase Activity ◽  
Caspase 8 ◽  
Activation Loop ◽  
Spontaneous Apoptosis ◽  
Apoptotic Pathway ◽  
Apoptosis Pathway ◽  
Luteal Regression ◽  
Kinase Activation

Receptor-interacting serine/threonine-protein kinase 3 (RIPK3) normally signals to necroptosis by phosphorylating MLKL. We report here that when the cellular RIPK3 chaperone Hsp90/CDC37 level is low, RIPK3 also signals to apoptosis. The apoptotic function of RIPK3 requires phosphorylation of the serine 165/threonine 166 sites on its kinase activation loop, resulting in inactivation of RIPK3 kinase activity while gaining the ability to recruit RIPK1, FADD, and caspase-8 to form a cytosolic caspase-activating complex, thereby triggering apoptosis. We found that PGF2α induces RIPK3 expression in luteal granulosa cells in the ovary to cause luteal regression through this RIPK3-mediated apoptosis pathway. Mice carrying homozygous phosphorylation-resistant RIPK3 S165A/T166A knockin mutations failed to respond to PGF2α but retained pro-necroptotic function, whereas mice with phospho-mimicking S165D/T166E homozygous knock-in mutation underwent spontaneous apoptosis in multiple RIPK3-expressing tissues and died shortly after birth. Thus, RIPK3 signals to either necroptosis or apoptosis depending on its serine 165/threonine 166 phosphorylation status.

scholarly journals Co-relation with novel phosphorylation sites of IκBα and necroptosis in breast cancer cells

BMC Cancer ◽  
2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Sung Hoon Choi ◽  
Hee-Sub Yoon ◽  
Shin-Ae Yoo ◽  
Sung Ho Yun ◽  
Joo-Hee Park ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Phosphorylation Site ◽  
Aurora Kinase ◽  
Serine Phosphorylation ◽  
Flight Mass Spectrometry ◽  
Iκb Kinase ◽  
Orbitrap Mass Spectrometer ◽  
Nf Kappab

Abstract Background Phosphorylation of NF-kappaB inhibitor alpha (IκBα) is key to regulation of NF-κB transcription factor activity in the cell. Several sites of IκBα phosphorylation by members of the IκB kinase family have been identified, but phosphorylation of the protein by other kinases remains poorly understood. We investigated a new phosphorylation site on IκBα and identified its biological function in breast cancer cells. Methods Previously, we observed that aurora kinase (AURK) binds IκBα in the cell. To identify the domains of IκBα essential for phosphorylation by AURK, we performed kinase assays with a series of IκBα truncation mutants. AURK significantly promoted activation of IκBα at serine 32 but not serine 36; by contrast, IκB kinase (IKK) family proteins activated both of these residues. We also confirmed phosphorylation of IκBα by matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF MS) and nano-liquid chromatography hybrid quadrupole orbitrap mass spectrometer (nanoLC-MS/MS; Q-Exactive). Results We identified two novel sites of serine phosphorylation, S63 and S262. Alanine substitution of S63 and S262 (S63A and S262A) of IκBα inhibited proliferation and suppressed p65 transcription activity. In addition, S63A and/or S262A of IκBα regulated apoptotic and necroptotic effects in breast cancer cells. Conclusions Phosphorylation of IκBα by AURK at novel sites is related to the apoptosis and necroptosis pathways in breast cancer cells.

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