scholarly journals rlk/TXK Encodes Two Forms of a Novel Cysteine String Tyrosine Kinase Activated by Src Family Kinases

1999 ◽  
Vol 19 (2) ◽  
pp. 1498-1507 ◽  
Author(s):  
Jayantha Debnath ◽  
Mario Chamorro ◽  
Michael J. Czar ◽  
Edward M. Schaeffer ◽  
Michael J. Lenardo ◽  
...  
Keyword(s):  
Tyrosine Kinases ◽  
Protein Localization ◽  
Cell Receptor ◽  
Src Family Kinases ◽  
The Other ◽  
Ph Domain ◽  
Acid Modification ◽  
Critical Determinant ◽  
Initiation Of Translation ◽  
Tcr Activation

ABSTRACT Rlk/Txk is a member of the BTK/Tec family of tyrosine kinases and is primarily expressed in T lymphocytes. Unlike other members of this kinase family, Rlk lacks a pleckstrin homology (PH) domain near the amino terminus and instead contains a distinctive cysteine string motif. We demonstrate here that Rlk protein consists of two isoforms that arise by alternative initiation of translation from the same cDNA. The shorter, internally initiated protein species lacks the cysteine string motif and is located in the nucleus when expressed in the absence of the larger form. In contrast, the larger form is cytoplasmic. We show that the larger form is palmitoylated and that mutation of its cysteine string motif both abolishes palmitoylation and allows the protein to migrate to the nucleus. The cysteine string, therefore, is a critical determinant of both fatty acid modification and protein localization for the larger isoform of Rlk, suggesting that Rlk regulation is distinct from the other Btk family kinases. We further show that Rlk is phosphorylated and changes localization in response to T-cell-receptor (TCR) activation and, like the other Btk family kinases, can be phosphorylated and activated by Src family kinases. However, unlike the other Btk family members, Rlk is activated independently of the activity of phosphatidylinositol 3-kinase, consistent with its lack of a PH domain. Thus, Rlk has two distinct isoforms, each of which may have unique properties in signaling downstream from the TCR.

scholarly journals GATA3 Abundance Is a Critical Determinant of T Cell Receptor β Allelic Exclusion

2017 ◽  
Vol 37 (12) ◽  
Author(s):  
Chia-Jui Ku ◽  
JoAnn M. Sekiguchi ◽  
Bharat Panwar ◽  
Yuanfang Guan ◽  
Satoru Takahashi ◽  
...  
Keyword(s):  
T Cell ◽  
T Cell Receptor ◽  
Cell Receptor ◽  
The Other ◽  
Allelic Exclusion ◽  
Wild Type ◽  
Critical Determinant ◽  
Gata3 Expression ◽  
Immunological Process ◽  
Functional Receptor

ABSTRACT Allelic exclusion describes the essential immunological process by which feedback repression of sequential DNA rearrangements ensures that only one autosome expresses a functional T or B cell receptor. In wild-type mammals, approximately 60% of cells have recombined the DNA of one T cell receptor β (TCRβ) V-to-DJ-joined allele in a functional configuration, while the second allele has recombined only the DJ sequences; the other 40% of cells have recombined the V to the DJ segments on both alleles, with only one of the two alleles predicting a functional TCRβ protein. Here we report that the transgenic overexpression of GATA3 leads predominantly to biallelic TCRβ gene (Tcrb) recombination. We also found that wild-type immature thymocytes can be separated into distinct populations based on intracellular GATA3 expression and that GATA3LO cells had almost exclusively recombined only one Tcrb locus (that predicted a functional receptor sequence), while GATA3HI cells had uniformly recombined both Tcrb alleles (one predicting a functional and the other predicting a nonfunctional rearrangement). These data show that GATA3 abundance regulates the recombination propensity at the Tcrb locus and provide new mechanistic insight into the historic immunological conundrum for how Tcrb allelic exclusion is mediated.

Biochemical and genetic analyses of the Tec kinases Itk and Rlk/Txk

2001 ◽  
Vol 29 (6) ◽  
pp. 863-867 ◽  
Author(s):  
M. J. Czar ◽  
J. Debnath ◽  
E. M. Schaeffer ◽  
C. M. Lewis ◽  
P. L. Schwartzberg
Keyword(s):  
Plasma Membrane ◽  
T Cell Receptor ◽  
Cell Receptor ◽  
Src Family Kinases ◽  
Signalling Pathways ◽  
Antigen Receptors ◽  
Ph Domain ◽  
Receptor Stimulation ◽  
Tec Kinases ◽  
Phosphoinositide 3 Kinase

The Tec kinases have been implicated as important components of signalling pathways downstream of lymphocyte antigen receptors. Activation of these kinases requires two steps: (i) phosphorylation by Src family kinases and (ii) plasma membrane localization, which is mediated by interaction between the pleckstrin homology (PH) domains of Tec kinases and the products of phosphoinositide-3 kinase (PI-3K). Itk and Rlk/Txk are Tec kinases expressed in T-lymphocytes. Despite similarity to other Tec kinases, Rlk/Txk lacks a PH domain and instead possesses a palmi-toylated cysteine-string motif. We have found that both Rlk/Txk and Itk are phosphorylated in response to T-cell receptor stimulation and can be activated by phosphorylation by Src family kinases. However, consistent with its lack of PH domain, Rlk/Txk is phosphorylated independent of PI-3K activity. Furthermore, we demonstrated that like Itk, Rlk/Txk is associated with lipid RAFTs (detergent-insoluble, cholesterol-rich regions of the membrane), but unlike Itk, Rlk/Txk's RAFT association is independent of PI-3K activity. Despite these differences, Rlk/Txk partially compensates for loss of Itk in gene-targeted animals, suggesting overlapping functions for these kinases.

scholarly journals The Glycine-Phenylalanine-Rich Region Determines the Specificity of the Yeast Hsp40 Sis1

1999 ◽  
Vol 19 (11) ◽  
pp. 7751-7758 ◽  
Author(s):  
Wei Yan ◽  
Elizabeth A. Craig
Keyword(s):  
Amino Acids ◽  
Molecular Chaperones ◽  
Rich Region ◽  
Critical Determinant ◽  
Unique Region ◽  
Chimeric Genes ◽  
F Region ◽  
Initiation Of Translation ◽  
J Domain ◽  
Essential Function

ABSTRACT Hsp40s are ubiquitous, conserved proteins which function with molecular chaperones of the Hsp70 class. Sis1 is an essential Hsp40 of the cytosol of Saccharomyces cerevisiae, thought to be required for initiation of translation. We carried out a genetic analysis to determine the regions of Sis1 required to perform its key function(s). A C-terminal truncation of Sis1, removing 231 amino acids but retaining the N-terminal 121 amino acids encompassing the J domain and the glycine-phenylalanine-rich (G-F) region, was able to rescue the inviability of a Δsis1 strain. The yeast cytosol contains other Hsp40s, including Ydj1. To determine which regions carried the critical determinants of Sis1 function, we constructed chimeric genes containing portions of SIS1 and YDJ1. A chimera containing the J domain of Sis1 and the G-F region of Ydj1 could not rescue the lethality of the Δsis1 strain. However, a chimera with the J domain of Ydj1 and the G/F region of Sis1 could rescue the strain’s lethality, indicating that the G-F region is a unique region required for the essential function of Sis1. However, a J domain is also required, as mutants expected to cause a disruption of the interaction of the J domain with Hsp70 are inviable. We conclude that the G-F region, previously thought only to be a linker or spacer region between the J domain and C-terminal regions of Hsp40s, is a critical determinant of Sis1 function.

The other T-cell receptor gene

Science ◽  
1984 ◽  
Vol 225 (4658) ◽  
pp. 155-155
Author(s):  
J. Marx
Keyword(s):  
T Cell ◽  
T Cell Receptor ◽  
Receptor Gene ◽  
Cell Receptor ◽  
The Other ◽  
T Cell Receptor Gene ◽  
Cell Receptor Gene

Stable association of pp60src and pp59fyn with the focal adhesion-associated protein tyrosine kinase, pp125FAK

1994 ◽  
Vol 14 (1) ◽  
pp. 147-155
Author(s):  
B S Cobb ◽  
M D Schaller ◽  
T H Leu ◽  
J T Parsons
Keyword(s):  
Focal Adhesion ◽  
Tyrosine Kinases ◽  
Protein Tyrosine Kinase ◽  
Src Family Kinases ◽  
Protein Tyrosine Kinases ◽  
Protein Tyrosine ◽  
Sh2 Domains ◽  
Embryo Cells ◽  
Stable Association

Changes in cellular growth and dramatic alterations in cell morphology and adhesion are common features of cells transformed by oncogenic protein tyrosine kinases, such as pp60src and other members of the Src family. In this report, we present evidence for the stable association of two Src family kinases (pp60src and pp59fyn) with tyrosine-phosphorylated forms of a focal adhesion-associated protein tyrosine kinase, pp125FAK. In Src-transformed chicken embryo cells, most of the pp125FAK was stably complexed with activated pp60src (e.g., pp60(527F). The stable association of pp125FAK with pp60(527F) in vivo required the structural integrity of the Src SH2 domain. The association of pp60(527F) and pp125FAK could be reconstituted in vitro by incubation of normal cell extracts with glutathione S-transferase fusion proteins containing SH2 or SH3/SH2 domains of pp60src. Furthermore, the association of isolated SH2 or SH3/SH2 domains with in vitro 32P-labeled pp125FAK protected the major site of pp125FAK autophosphorylation from digestion with a tyrosine phosphatase, indicating that the autophosphorylation site of pp125FAK participates in binding with Src. Immunoprecipitation of Src family kinases from extracts of normal chicken embryo cells revealed stable complexes of pp59fyn and tyrosine-phosphorylated pp125FAK. These data provide evidence for a direct interaction between two cytoplasmic nonreceptor protein tyrosine kinases and suggest that Src may contribute to changes in pp125FAK regulation in transformed cells. Furthermore, pp125FAK may directly participate in the targeting of pp59fyn or possibly other Src family kinases to focal adhesions in normal cells.

scholarly journals Genetic variants of human red-cell membrane sialoglycoprotein β. Study of the alterations occurring in the sialoglycoprotein-β gene

1988 ◽  
Vol 250 (2) ◽  
pp. 407-414 ◽  
Author(s):  
M J Tanner ◽  
S High ◽  
P G Martin ◽  
D J Anstee ◽  
P A Judson ◽  
...  
Keyword(s):  
Genetic Variants ◽  
Southern Blotting ◽  
Protein Product ◽  
Red Cells ◽  
The Other ◽  
Red Cell ◽  
Red Cell Membrane ◽  
Initiation Of Translation ◽  
Beta Gene ◽  
Human Red Cell Membrane

We have studied the DNA of individuals who express an altered sialoglycoprotein beta on their red cells by using Southern blotting with sialoglycoprotein-beta cDNA probes. Individuals of the Leach phenotype do not express any beta (sialoglycoprotein beta) or gamma (sialoglycoprotein gamma) on their red cells, and we show that about 7 kb of DNA, including the 3′ end of the beta gene, is deleted in this DNA. Any protein product of this gene is likely to lack the membrane-associating domain of beta. We have also examined the DNA of two types of other individuals (Yus-type and Gerbich-type) who have red cells that lack beta and gamma, but contain abnormal sialoglycoproteins related to beta. These two types of DNA contain different internal deletions of about 6 kb in the beta gene. We suggest that these deletions result from the presence of two different sets of internal homology in the beta gene, and on this basis we propose structures for the abnormal Yus-type and Gerbich-type sialoglycoproteins which are consistent with the other evidence that is available. We provide evidence that beta and gamma are products of the same gene and suggest a possible mechanism for the origin of gamma based on leaky initiation of translation of beta mRNA.

scholarly journals Commitment of Common T/Natural Killer (Nk) Progenitors to Unipotent T and Nk Progenitors in the Murine Fetal Thymus Revealed by a Single Progenitor Assay

1999 ◽  
Vol 190 (11) ◽  
pp. 1617-1626 ◽  
Author(s):  
Tomokatsu Ikawa ◽  
Hiroshi Kawamoto ◽  
Shinji Fujimoto ◽  
Yoshimoto Katsura
Keyword(s):  
T Cell ◽  
Nk Cells ◽  
Natural Killer ◽  
T Cell Receptor ◽  
Cell Lineage ◽  
Cell Receptor ◽  
The Other ◽  
Fetal Thymus ◽  
Β Chain ◽  
Clonal Assay

We have established a new clonal assay system that can evenly support the development of T and natural killer (NK) cells. With this system, we show that all T cell progenitors in the earliest CD44+CD25−FcγRII/III− fetal thymus (FT) cell population retain NK potential, and that the NK lineage–committed progenitors (p-NK) also exist in this population. T cell lineage–committed progenitors (p-T), which are unable to generate NK cells, first appear at the CD44+CD25− FcγRII/III+ stage in day 12 FT. The proportion of p-T markedly increases during the transition from the CD44+CD25− stage to the CD44+CD25+ stage in day 14 FT. On the other hand, p-NK preferentially increase in number at the CD44+CD25− stage between days 12 and 14 of gestation. The production of p-NK continues up to the CD44+CD25+ stage, but ceases before the rearrangement of T cell receptor β chain genes. It was further shown that the CD44+CD25− CD122+ population of day 14 FT exclusively contains p-NK. These results indicate that the earliest T cell progenitor migrating into the FT is T/NK bipotent, and strongly suggest that the bipotent progenitor continuously produces p-NK and p-T until the CD44+CD25+ stage.

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