Arabidopsis MLK3, a Plant-specific Casein Kinase 1, Negatively Regulated Flowering and Phosphorylated Histone H3 in vivo

2019 ◽  
Author(s):  
Zhen Wang ◽  
Junmei Kang ◽  
Shangang Jia ◽  
Tiejun Zhang ◽  
Zhihai Wu ◽  
...  

Abstract Background: Casein kinase 1 (CK1) family members are highly conserved serine/threonine kinase present in most eukaryotes with multiple biological functions. Arabidopsis MUT9-like kinases ( MLKs ) belong to a clade CK1 specific to the plant kingdom and have been implicated collectively in modulating flowering related processes. Three of the four MLKs ( MLK1/2/4 ) have been characterized, however, little is known about MLK3 , the most divergent MLKs. Results: We demonstrated that compared with wild type, mlk3 , a truncated MLK3 , flowered slightly early under long day conditions and ectopic expression of MLK3 rescued the morphological defects of mlk3 , indicating that MLK3 negatively regulates flowering. GA 3 application accelerated flowering of both wild type and mlk3 , suggesting that mlk3 had normal GA response. The recombinant MLK3-GFP was localized in the nucleus exclusively. In vitro kinase assay revealed that the nuclear protein MLK3 phosphorylated histone 3 at threonine 3 (H3T3ph). Mutation of a conserved catalytic residue (Lysine 175) abolished the kinase activity and resulted in failure to complement the early flowering phenotype of mlk3 . Interestingly, the global level of H3T3 phosphorylation in mlk3 did not differ significantly from wild type, suggesting the redundant roles of MLKs in flowering regulation. The transcriptomic analysis demonstrated that 425 genes significantly altered expression level in mlk3 relative to wild type. The mlk3 mlk4 double mutant generated by crossing mlk3 with mlk4 , a loss-of-function mutant of MLK4 showing late flowering, flowered between the two parental lines, suggesting that MLK3 played an antagonistic role to MLK4 in plant transition to flowering. Conclusions: A serine/threonine kinase encoding gene MLK3 is a casein kinase 1 specific to the plant species and represses flowering slightly. MLK3 located in nucleus catalyzes the phosphorylation of histone H3 at threonine 3 in vitro and an intact lysine residue (K175) is indispensible for the kinase activity. This study sheds new light on the delicate control of flowering by the plant-specific CK1 in Arabidopsis.

1996 ◽  
Vol 16 (3) ◽  
pp. 998-1005 ◽  
Author(s):  
J Liu ◽  
Y Wu ◽  
G Z Ma ◽  
D Lu ◽  
L Haataja ◽  
...  

The first exon of the BCR gene encodes a new serine/threonine protein kinase. Abnormal fusion of the BCR and ABL genes, resulting from the formation of the Philadelphia chromosome (Ph), is the hallmark of Ph-positive leukemia. We have previously demonstrated that the Bcr protein is tyrosine phosphorylated within first-exon sequences by the Bcr-Abl oncoprotein. Here we report that in addition to tyrose 177 (Y-177), Y-360 and Y283 are phosphorylated in Bcr-Abl proteins in vitro. Moreover, Bcr tyrosine 360 is phosphorylated in vivo within both Bcr-Abl and Bcr. Bcr mutant Y177F had a greatly reduced ability to transphosphorylate casein and histone H1, whereas Bcr mutants Y177F and Y283F had wild-type activities. In contrast, the Y360F mutation had little effect on Bcr's autophosphorylation activity. Tyrosine-phosphorylated Bcr, phosphorylated in vitro by Bcr-Abl, was greatly inhibited in its serine/threonine kinase activity, impairing both auto- and transkinase activities of Bcr. Similarly, the isolation of Bcr from cells expressing Bcr-Abl under conditions that preserve phosphotyrosine residues also reduced Bcr's kinase activity. These results indicate that tyrosine 360 of Bcr is critical for the transphosphorylation activity of Bcr and that in Ph-positive leukemia, Bcr serine/threonine kinase activity is seriously impaired.


2019 ◽  
Vol 10 (12) ◽  
Author(s):  
Song-Yi Lee ◽  
Hyunjoo Kim ◽  
Cathena Meiling Li ◽  
Jaemin Kang ◽  
Ayaz Najafov ◽  
...  

AbstractUpon necroptosis activation, receptor interacting serine/threonine kinase (RIPK)1 and RIPK3 form a necrosome complex with pseudokinase mixed lineage kinase-like (MLKL). Although protein phosphorylation is a key event for RIPK1 and RIPK3 activation in response to a necroptosis signal, relatively little is known about other factors that might regulate the activity of these kinases or necrosome formation. Through a gain-of-function screen with 546 kinases and 127 phosphatases, we identified casein kinase 1 gamma (CK1γ) as a candidate necroptosis-promoting factor. Here, we show that the decreased activity or amounts of CK1γ1 and CK1γ3, either by treatment with a chemical inhibitor or knockdown in cells, reduced TNFα-induced necroptosis. Conversely, ectopic expression of CK1γ1 or CK1γ3 exacerbated necroptosis, but not apoptosis. Similar to RIPK1 and RIPK3, CK1γ1 was also cleaved at Asp343 by caspase-8 during apoptosis. CK1γ1 and CK1γ3 formed a protein complex and were recruited to the necrosome harboring RIPK1, RIPK3 and MLKL. In particular, an autophosphorylated form of CK1γ3 at Ser344/345 was detected in the necrosome and was required to mediate the necroptosis. In addition, in vitro assays with purified proteins showed that CK1γ phosphorylated RIPK3, affecting its activity, and in vivo assays showed that the CK1γ-specific inhibitor Gi prevented abrupt death in mice with hypothermia in a model of TNFα-induced systemic inflammatory response syndrome. Collectively, these data suggest that CK1γ1 and CK1γ3 are required for TNFα-induced necroptosis likely by regulating RIPK3.


2017 ◽  
Vol 37 (6) ◽  
Author(s):  
Ghanshyam S. Yadav ◽  
Sandeep K. Ravala ◽  
Sangita Kachhap ◽  
Meghna Thakur ◽  
Abhishek Roy ◽  
...  

Guanylate kinase is an essential and conserved enzyme in nucleotide biosynthetic pathway that transfers phosphoryl group of ATP to GMP for yielding GDP. Here, we report the phosphorylation of guanylate kinase from Mycobacterium tuberculosis (mGmk) by eukaryotic-type Ser/Thr kinase, PknA. Mass spectrometric studies identified Thr101 and Thr169 as phosphorylatable residues in mGmk. To evaluate the significance of phosphorylation in these threonines, two point (T101A and T169A) and one double (T101A-T169A) mutants were generated. The kinase assay with these mutant proteins revealed the major contribution of Thr169 compared with Thr101 in the phosphorylation of mGmk. Kinetic analysis indicated that p-mGmk was deficient in its enzymatic activity compared with that of its un-phosphorylated counterpart. Surprisingly, its phosphoablated (T169A) as well as phosphomimic (T169E) variants exhibited decreased activity as was observed with p-mGmk. Structural analysis suggested that phosphorylation of Thr169 might affect its interaction with Arg166, which is crucial for the functioning of mGmk. In fact, the R166A and R166K mutant proteins displayed a drastic decrease in enzymatic activity compared with that of the wild-type mGmk. Molecular dynamics (MD) studies of mGmk revealed that upon phosphorylation of Thr169, the interactions of Arg165/Arg166 with Glu158, Asp121 and residues of the loop in GMP-binding domain are perturbed. Taken together, our results illuminate the mechanistic insights into phosphorylation-mediated modulation of the catalytic activity of mGmk.


1996 ◽  
Vol 16 (4) ◽  
pp. 1401-1409 ◽  
Author(s):  
R Lin ◽  
P Beauparlant ◽  
C Makris ◽  
S Meloche ◽  
J Hiscott

The NF-kappaB/Rel transcription factors participate in the activation of immune system regulatory genes and viral early genes including the human immunodeficiency virus type 1 long terminal repeat. NF-kappaB/Rel proteins are coupled to inhibitory molecules, collectively termed IkappaB, which are responsible for cytoplasmic retention of NF-kappaB. Cell activation leads to the phosphorylation and degradation of IkappaBalpha, permitting NG-kappaB/Rel translocation to the nucleus and target gene activation. To further characterize the signaling events that contribute to IkappaBalpha phosphorylation, a kinase activity was isolated from Jurkat T cells that specifically interacted with IkappaBalpha in an affinity chromatography step and phosphorylated IkappaBalpha with high specificity in vitro. By using an in-gel kinase assay with recombinant IkappaBalpha as substrate, two forms of the kinase (43 and 38 kDa) were identified. Biochemical criteria and immunological cross-reactivity identified the kinase activity as the alpha catalytic subunit of casein kinase II (CKII). Deletion mutants of IkappaBalpha delta1 to delta4) localized phosphorylation to the C-terminal PEST domain of IkappaBalpha. Point mutation of residues T-291, S-283, and T-299 dramatically reduced phosphorylation of IkappaBalpha by the kinase in vitro. NIH-3T3 cells that stably expressed wild-type IkappaBalpha (wtIkappaB), double-point-mutated IkappaBalpha (T291A, S283A), or triple-point-mutated IkappaBalpha (T291A, S283A, T299A) under the control of the tetracycline-responsive promoter were generated. Constitutive phosphorylation of the triple point mutant was eliminated in vivo, although tumor necrosis factor-inducible IkappaBalpha degradation was unaffected. In cell lines and in transiently transfected cells, mutation of the CKII sites in IkappaBalpha resulted in a protein with increased intrinsic stability. Together with results demonstrating a role for N-terminal sites in inducer-mediated phosphorylation and degradation of IkappaBalpha, these studies indicate that CKII sites in the C-terminal PEST domain are important for constitutive phosphorylation and intrinsic stability of IkappaBalpha.


Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 942-942 ◽  
Author(s):  
Yingqiu Xie ◽  
Mehmet Burcu ◽  
Maria R. Baer

Abstract Abstract 942 Fms-like tyrosine kinase 3 (FLT3) internal tandem duplication (ITD) results in FLT3 constitutive activation and aberrant signaling in acute myeloid leukemia (AML) cells. FLT3-ITD is associated with adverse treatment outcome in AML, but FLT3 inhibitors have had limited therapeutic efficacy. The oncogenic serine/threonine kinase Pim-1 is upregulated in AML cells with FLT3-ITD. Pim-1 inhibitors are entering clinical trials, and we sought to characterize the role of Pim-1 and the effects of Pim-1 inhibition in FLT3-ITD cells. Wild-type (WT) FLT3 exists predominantly in a 150 kDa complex glycosylated form. In contrast, FLT3-ITD is partially retained in the endoplasmic reticulum (ER) as a misfolded 130 kDa underglycosylated, or high-mannose, species in association with the ER transmembrane chaperone calnexin. In addition, FLT3-ITD also associates with and is stabilized by the cytosolic chaperone heat shock protein (HSP) 90. FLT3-ITD activates signal transducer and activation of transcription (STAT) 5 and upregulates the STAT5 downstream target Pim-1. FLT3 contains a putative Pim-1 substrate consensus serine phosphorylation site, and we hypothesized that FLT3 might be a Pim-1 substrate. FLT3-ITD cell lines studied included MV4-11, MOLM-14 and transfected Ba/F3-ITD, and FLT3 WT cells included BV173, EOL-1 and transfected Ba/F3-WT. Pim-1 activity was measured by an in vitro kinase assay of BAD phosphorylation at serine 112, and Pim-1 expression, FLT3 expression, phosphorylation and co-immunoprecipitation, and STAT5 phosphorylation and expression by Western blot analysis. Pim-1 knockdown was accomplished by infection with lentivirus containing Pim-1 small hairpin RNA (shRNA) or non-target control, and Pim-1 kinase inhibition by incubation with the Pim-1-selective inhibitor quercetagetin. Pim-1 was found to directly interact with and serine-phosphorylate FLT3 from FLT3-ITD, but not FLT3-WT, cells in vitro. Inhibition of Pim-1 kinase disrupted binding of FLT3 to its chaperones calnexin and HSP90, and resulted in decreased expression and half-life of 130 kDa FLT3 and increased expression and half-life of 150 kDa FLT3. The decrease in expression and half-life of 130 kDa FLT3 was partially abrogated by co-incubation with the proteasome inhibitor MG132. Moreover, the increase in 150 Kda FLT3 was abrogated by co-incubation with the glycosylation inhibitor 2-deoxy-D-glucose. Thus Pim-1 maintains FLT3 as a 130 kDa species by enhancing its binding to its chaperones calnexin and HSP90, protecting it from proteasomal degradation and inhibiting its glycosylation to form 150 kDa FLT3. Inhibition of Pim-1 kinase activity also decreased phosphorylation of FLT3 at tyrosine 591, a docking site for binding of FLT3-ITD, but not FLT3-WT, to STAT5, and decreased both STAT5 phosphorylation and expression of Pim-1 itself. In contrast, Pim-1 inhibition had no effect on FLT3 tyrosine kinase activity nor on expression of Pim-2, another Pim kinase family member implicated in promoting survival of FLT3-ITD cells. Finally, the Pim-1 kinase inhibitor quercetagetin and the FLT3 inhibitor PKC412 had a synergistic effect in inducing apoptosis of Ba/F3-ITD cells: We conclude that Pim-1, which is transcriptionally upregulated through STAT5 in FLT3-ITD cells, serine-phosphorylates FLT3-ITD, thereby maintaining it in an underglycosylated form, and promotes STAT5 signaling, and that inhibition of Pim-1 and of FLT3 is synergistic in inducing apoptosis of FLT3-ITD cells. Thus Pim-1 inhibitors should inhibit aberrant signaling upstream as well as downstream of Pim-1 in FLT3-ITD cells, and have the potential to enhance the therapeutic efficacy of FLT3 inhibitors in patients with AML with FLT3-ITD Disclosures: No relevant conflicts of interest to declare.


2016 ◽  
Vol 27 (7) ◽  
pp. 1069-1084 ◽  
Author(s):  
Jessica Konen ◽  
Scott Wilkinson ◽  
Byoungkoo Lee ◽  
Haian Fu ◽  
Wei Zhou ◽  
...  

LKB1 is a serine/threonine kinase and a commonly mutated gene in lung adenocarcinoma. The majority of LKB1 mutations are truncations that disrupt its kinase activity and remove its C-terminal domain (CTD). Because LKB1 inactivation drives cancer metastasis in mice and leads to aberrant cell invasion in vitro, we sought to determine how compromised LKB1 function affects lung cancer cell polarity and invasion. Using three-dimensional models, we show that LKB1 kinase activity is essential for focal adhesion kinase–mediated cell adhesion and subsequent collagen remodeling but not cell polarity. Instead, cell polarity is overseen by the kinase-independent function of its CTD and more specifically its farnesylation. This occurs through a mesenchymal-amoeboid morphological switch that signals through the Rho-GTPase RhoA. These data suggest that a combination of kinase-dependent and -independent defects by LKB1 inactivation creates a uniquely invasive cell with aberrant polarity and adhesion signaling that drives invasion into the microenvironment.


Genes ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 345 ◽  
Author(s):  
Junmei Kang ◽  
Huiting Cui ◽  
Shangang Jia ◽  
Wenwen Liu ◽  
Renjie Yu ◽  
...  

Arabidopsis thaliana MUT9-LIKE KINASES (MLKs), a family of the plant-specific casein kinase 1 (CK1), have been implicated collectively in multiple biological processes including flowering. Three of the four MLKs (MLK1/2/4) have been characterized, however, little is known about MLK3, the most divergent member of MLKs. Here, we demonstrated that disruption of MLK3 transcript in mlk3 caused early flowering with retarded leaf growth under long-day conditions. In vitro kinase assay showed the nuclear protein MLK3 phosphorylated histone 3 at threonine 3 (H3T3) and mutation of a conserved residue (K146R) abolished the catalytic activity. Ectopic expression of MLK3 but not MLK3(K146R) rescued the morphological defects of mlk3, indicating that an intact MLK3 is critical for maintaining proper flowering time. Transcriptomic analysis revealed that the floral repressor FLOWERING LOCUS C (FLC) was down-regulated significantly in mlk3, suggesting that MLK3 negatively regulates flowering. Hence, MLK3 plays a role in repressing the transition from vegetative to reproductive phase in A. thaliana. This study sheds light on the delicate control of flowering time by A. thaliana CK1 specific to the plant kingdom.


1996 ◽  
Vol 109 (7) ◽  
pp. 1847-1856 ◽  
Author(s):  
J.A. Santos ◽  
E. Logarinho ◽  
C. Tapia ◽  
C.C. Allende ◽  
J.E. Allende ◽  
...  

We report the molecular cloning and characterisation of the first CK1(casein kinase) gene of Drosophila melanogaster (dmCK1). The protein sequence (DMCK1) shares significant homology with other mammalian CK1 protein kinases of the alpha sub-class. The dmCK1 gene is expressed only in adult females and during early embryonic development as a single transcript. Western blot analysis of total protein extracts of different stages of development show that the gene product is likewise present during early embryogenesis and in adult females. Kinase activity studies show that DMCK1 is active when in vitro translated but inactive when immunoprecipitated from total early embryo extracts. However, after dephosphorylation treatment the immunoprecipitates show high kinase activity. More significantly, DMCK1 kinase activity present in the immunoprecipitates can be specifically activated by gamma-irradiation of early embryos. Also, when DMCK1 is immunoprecipitated after irradiation it appears to undergo phosphorylation. Immunolocalization of DMCK1 in early embryos shows that the protein is predominantly cytoplasmic but after irradiation there is a significant relocalization to the interphase nucleus. The results suggest a possible requirement of the Drosophila CK1 alpha for mechanisms associated with DNA repair during early embryogenesis.


1999 ◽  
Vol 144 (1) ◽  
pp. 71-82 ◽  
Author(s):  
Guisheng Zeng ◽  
Mingjie Cai

Normal actin cytoskeleton organization in budding yeast requires the function of the Pan1p/ End3p complex. Mutations in PAN1 and END3 cause defects in the organization of actin cytoskeleton and endocytosis. By screening for mutations that can suppress the temperature sensitivity of a pan1 mutant (pan1-4), a novel serine/threonine kinase Prk1p is now identified as a new factor regulating the actin cytoskeleton organization in yeast. The suppression of pan1-4 by prk1 requires the presence of mutant Pan1p. Although viable, the prk1 mutant is unable to maintain an asymmetric distribution of the actin cytoskeleton at 37°C. Consistent with its role in the regulation of actin cytoskeleton, Prk1p localizes to the regions of cell growth and coincides with the polarized actin patches. Overexpression of the PRK1 gene in wild-type cells leads to lethality and actin cytoskeleton abnormalities similar to those exhibited by the pan1 and end3 mutants. In vitro phosphorylation assays demonstrate that Prk1p is able to phosphorylate regions of Pan1p containing the LxxQxTG repeats, including the region responsible for binding to End3p. Based on these findings, we propose that the Prk1 protein kinase regulates the actin cytoskeleton organization by modulating the activities of some actin cytoskeleton-related proteins such as Pan1p/End3p.


Author(s):  
Shengjun Zhang ◽  
Minli Liu ◽  
Haoyu Wu ◽  
Kaiyu Wang

: Serine/threonine kinase 33 (STK33) is a serine/threonine kinase, and participates in many apoptotic process. Herein, we found that the extracellular signal-regulated kinase 2 (ERK2) was a substrate of STK33. STK33 phosphorylated ERK2and increased the activity of ERK2 and promote the tumorigenesis of colorectal cancer HCT15 cells. Clinical simple showed that STK33 was highly expression in colorectal cells and tissues. Ex vivo and in vivo studies demonstrated that STK33 accelerate tumorigenic properties in JB6C141 cells and athymic nude rats. In vitro kinase assay results indicated that STK33 can phosphorylate ERK2. Ex vivo studies further showed that STK33 can bind with ERK2 and take part in the regulation of ERKs signaling pathway. In short, our results showed that STK33 is a novel upstream kinase of ERK2. It may provide a better prospect for STK33 based prevention and treatment for colorectal cancer patients.


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