Biomedical subjects

Lutz Tautz

Publications and source records attributed to Lutz Tautz.

13 recordsLinked to original sources

PubMed2006

Lipid raft targeting of hematopoietic protein tyrosine phosphatase by protein kinase C theta-mediated phosphorylation.

Protein kinase C theta (PKC theta) is unique among PKC isozymes in its translocation to the center of the immune synapse in T cells and its unique downstream signaling. Here we show that the hematopoietic protein tyrosine phosphatase (HePTP) also accumulates in the immune synapse in a PKC theta-dependent manner upon antigen recognition by T cells and is phosphorylated by PKC theta at Ser-225, which is required for lipid raft translocation. Immune synapse translocation was completely absent in antigen-specific T cells from PKC theta-/- mice. In intact T cells, HePTP-S225A enhanced T-cell receptor (TCR)-induced NFAT/AP-1 transactivation, while the acidic substitution mutant was as efficient as wild-type HePTP. We conclude that HePTP is phosphorylated in the immune synapse by PKC theta and thereby targeted to lipid rafts to temper TCR signaling. This represents a novel mechanism for the active immune synapse recruitment and activation of a phosphatase in TCR signaling.

Animals↗

PubMed2006

Targeting the PTPome in human disease.

Protein tyrosine phosphatases (PTPs) play vital roles in numerous cellular processes and are implicated in a growing number of human diseases, ranging from cancer to cardiovascular, immunological, infectious, neurological and metabolic diseases. There are at least 107 genes in the human genome, collectively referred to as the human 'PTPome'. Here the authors review the involvement of PTPs in human disease, discuss their potential as drug targets, and current efforts to develop PTP inhibitors for the treatment of human disease. Finally, the authors present their view of the future for PTPs as drug targets.

Disease↗

PubMed2005

Autoimmune-associated lymphoid tyrosine phosphatase is a gain-of-function variant.

A SNP in the gene PTPN22 is associated with type 1 diabetes, rheumatoid arthritis, lupus, Graves thyroiditis, Addison disease and other autoimmune disorders. T cells from carriers of the predisposing allele produce less interleukin-2 upon TCR stimulation, and the encoded phosphatase has higher catalytic activity and is a more potent negative regulator of T lymphocyte activation. We conclude that the autoimmune-predisposing allele is a gain-of-function mutant.

Alleles↗

PubMed2005

Structure of the hematopoietic tyrosine phosphatase (HePTP) catalytic domain: structure of a KIM phosphatase with phosphate bound at the active site.

Hematopoietic tyrosine phosphatase (HePTP) is a 38kDa class I non-receptor protein tyrosine phosphatase (PTP) that is strongly expressed in T cells. It is composed of a C-terminal classical PTP domain (residues 44-339) and a short N-terminal extension (residues 1-43) that functions to direct HePTP to its physiological substrates. Moreover, HePTP is a member of a recently identified family of PTPs that has a major role in regulating the activity and translocation of the MAP kinases Erk and p38. HePTP binds Erk and p38 via a short, highly conserved motif in its N terminus, termed the kinase interaction motif (KIM). Association of HePTP with Erk via the KIM results in an unusual, reciprocal interaction between the two proteins. First, Erk phosphorylates HePTP at residues Thr45 and Ser72. Second, HePTP dephosphorylates Erk at PTyr185. In order to gain further insight into the interaction of HePTP with Erk, we determined the structure of the PTP catalytic domain of HePTP, residues 44-339. The HePTP catalytic phosphatase domain displays the classical PTP1B fold and superimposes well with PTP-SL, the first KIM-containing phosphatase solved to high resolution. In contrast to the PTP-SL structure, however, HePTP crystallized with a well-ordered phosphate ion bound at the active site. This resulted in the closure of the catalytically important WPD loop, and thus, HePTP represents the first KIM-containing phosphatase solved in the closed conformation. Finally, using this structure of the HePTP catalytic domain, we show that both the phosphorylation of HePTP at Thr45 and Ser72 by Erk2 and the dephosphorylation of Erk2 at Tyr185 by HePTP require significant conformational changes in both proteins.

Amino Acid Motifs↗

PubMed2005

Yersinia phosphatase induces mitochondrially dependent apoptosis of T cells.

To evade the immune system, the etiologic agent of plague, Yersinia pestis, injects an exceptionally active tyrosine phosphatase called YopH into host cells using a type III secretion system. We recently reported that YopH acutely inhibits T cell antigen receptor signaling by dephosphorylating the Lck tyrosine kinase. Here, we show that prolonged presence of YopH in primary T cells or Jurkat T leukemia cells causes apoptosis, detected by annexin V binding, mitochondrial breakdown, caspase activation, and internucleosomal fragmentation. YopH also causes cell death when expressed in HeLa cells, and this cell death was inhibited by YopH-specific small molecule inhibitors. Cell death induced by YopH was also prevented by caspase inhibition or co-expression of Bcl-xL. We conclude that YopH not only paralyzes T cells acutely, but also ensures that the cells will not recover to induce a protective immune response but instead undergo mitochondrially regulated programmed cell death.

Annexin A5↗

PubMed2005

In vitro characterization of the Bacillus subtilis protein tyrosine phosphatase YwqE.

Both gram-negative and gram-positive bacteria possess protein tyrosine phosphatases (PTPs) with a catalytic Cys residue. In addition, many gram-positive bacteria have acquired a new family of PTPs, whose first characterized member was CpsB from Streptococcus pneumoniae. Bacillus subtilis contains one such CpsB-like PTP, YwqE, in addition to two class II Cys-based PTPs, YwlE and YfkJ. The substrates for both YwlE and YfkJ are presently unknown, while YwqE was shown to dephosphorylate two phosphotyrosine-containing proteins implicated in UDP-glucuronate biosynthesis, YwqD and YwqF. In this study, we characterize YwqE, compare the activities of the three B. subtilis PTPs (YwqE, YwlE, and YfkJ), and demonstrate that the two B. subtilis class II PTPs do not dephosphorylate the physiological substrates of YwqE.

Amino Acid Sequence↗

PubMed2005

Low-molecular-weight protein tyrosine phosphatases of Bacillus subtilis.

In gram-negative organisms, enzymes belonging to the low-molecular-weight protein tyrosine phosphatase (LMPTP) family are involved in the regulation of important physiological functions, including stress resistance and synthesis of the polysaccharide capsule. LMPTPs have been identified also in gram-positive bacteria, but their functions in these organisms are presently unknown. We cloned two putative LMPTPs from Bacillus subtilis, YfkJ and YwlE, which are highly similar to each other in primary structure as well as to LMPTPs from gram-negative bacteria. When purified from overexpressing Escherichia coli strains, both enzymes were able to dephosphorylate p-nitrophenyl-phosphate and phosphotyrosine-containing substrates in vitro but showed significant differences in kinetic parameters and sensitivity to inhibitors. Transcriptional analyses showed that yfkJ was transcribed at a low level throughout the growth cycle and underwent a sigma(B)-dependent transcriptional upregulation in response to ethanol stress. The transcription of ywlE was growth dependent but stress insensitive. Genomic deletion of each phosphatase-encoding gene led to a phenotype of reduced bacterial resistance to ethanol stress, which was more marked in the ywlE deletion strain. Our study suggests that YfkJ and YwlE play roles in B. subtilis stress resistance.

Amino Acid Sequence↗

PubMed2004

Inhibition of Yersinia tyrosine phosphatase by furanyl salicylate compounds.

To avoid detection and targeting by the immune system, the plague-causing bacterium Yersinia pestis uses a type III secretion system to deliver a set of inhibitory proteins into the cytoplasm of immune cells. One of these proteins is an exceptionally active tyrosine phosphatase termed YopH, which paralyzes lymphocytes and macrophages by dephosphorylating critical tyrosine kinases and signal transduction molecules. Because Y. pestis strains lacking YopH are avirulent, we set out to develop small molecule inhibitors for YopH. We used a novel and cost-effective approach, in which leads from a chemical library screening were analyzed and computationally docked into the crystal structure of YopH. This resulted in the identification of a series of novel YopH inhibitors with nanomolar Ki values, as well as the structural basis for inhibition. Our inhibitors lack the polar phosphate-mimicking moiety of rationally designed tyrosine phosphatase inhibitors, and they readily entered live cells and rescued them from YopH-induced tyrosine dephosphorylation, signaling paralysis, and cell death. These inhibitors may become useful for treating the lethal infection by Y. pestis.

Bacterial Outer Membrane Proteins↗

PubMed2004

Covalent decoration of multi-walled carbon nanotubes with silica nanoparticles.

We describe a novel tunable approach for the synthesis of carbon nanotube-silica nanobead composites. The control of nanotube morphology and bead size coupled with the versatility of silica chemistry makes these structures an excellent platform for the development of biosensors, or for optical, magnetic and catalytic applications.

Crystallization↗

PubMed2004

The minimal essential core of a cysteine-based protein-tyrosine phosphatase revealed by a novel 16-kDa VH1-like phosphatase, VHZ.

The smallest active protein-tyrosine phosphatase yet (only 16 kDa) is described here and given the name VHZ for VH1-like member Z because it belongs to the group of small Vaccinia virus VH1-related dual specific phosphatases exemplified by VHR, VHX, and VHY. Human VHZ is remarkably well conserved through evolution as it has species orthologs in frogs, fish, fly, and Archaea. The gene for VHZ, which we designate as DUSP25, is located on human chromosome 1q23.1 and consists of only two coding exons. VHZ is broadly expressed in tissues and cells, including resting blood lymphocytes, Jurkat T cells, HL-60, and RAMOS. In transfected cells, VHZ was located in the cytosol and in other cells also in the nucleoli. Endogenous VHZ showed a similar but more granular distribution. We show that VHZ is an active phosphatase and analyze its structure by computer modeling, which shows that in comparison with the 185-amino acid residue VHR, the 150-residue VHZ is a shortened version of VHR and contains the minimal set of secondary structure elements conserved in all known phosphatases from this class. The surface charge distribution of VHZ differs from that of VHR and is therefore unlikely to dephosphorylate mitogen-activated protein kinases. The remarkably high degree of conservation of VHZ through evolution may indicate a role in some ancient and fundamental physiological process.

Amino Acid Sequence↗

PubMed2004

VHY, a novel myristoylated testis-restricted dual specificity protein phosphatase related to VHX.

The human DUSP15 gene encodes an uncharacterized 235-amino acid member of the subfamily of small dual specificity protein phosphatases related to the Vaccinia virus VH1 phosphatase. Similar to VHR-related MKPX (VHX) (DUSP22), the predicted protein has an N-terminal myristoylation recognition sequence, and we show here that both are indeed modified by the attachment of a myristate to Gly-2. In recognition of this relatedness to VHX, we refer to the DUSP15-encoded protein as VH1-related member Y (VHY). We report that VHY is expressed at high levels in the testis and barely detectable levels in the brain, spinal cord, and thyroid. A VHY-specific antiserum detected a protein with an apparent molecular mass of 26 kDa, and histochemical analysis showed that VHY was readily detectable in pachytene spermatocytes (midstage of meiotic division I) and round spermatids and weakly in Leydig cells (somatic cells outside of the seminiferous tubules). When expressed in 293T or NIH-3T3 cells, VHY was concentrated at the plasma membrane with some staining of vesicular structures in the Golgi region. Mutation of the myristoylation site Gly-2 abrogated membrane location. Finally, we demonstrate that VHY is an active phosphatase in vitro. We conclude that VHY is a new member of a subgroup of myristoylated VH1-like small dual specificity phosphatases.

Amino Acid Motifs↗

PubMed2004

Protein tyrosine phosphatases in T cell physiology.

The molecular mechanisms of signal transduction have been the focus of intense research during the last decade. In T cells, much of the work has centered on protein tyrosine kinase-mediated signaling from the TCR and cytokine receptors, while the study of protein tyrosine phosphatases has lagged behind. Nevertheless, it has now become clear that many protein tyrosine phosphatases play equally important roles in T cell physiology and that no kinase-regulated system would work without the counterbalancing participation of phosphatases. In fact, we have learned that many processes are regulated primarily on the phosphatase side. This minireview summarizes the current state-of-the art in our understanding of the regulation and biology of protein tyrosine phosphatases in T lymphocyte physiology.

Dual Specificity Phosphatase 3↗

PubMed2004

NMR-based techniques in the hit identification and optimisation processes.

In this review, the use of general NMR spectroscopy techniques to detect ligand binding and to monitor enzyme kinetics and inhibition, which appear particularly useful in hit identification and validation, is reiterated. Furthermore, the use of NMR-based strategies for lead optimisations that are based on either iterative derivatisations of an initial core structure or on linking fragments that occupy adjacent pockets in the target's binding site will also be described. Several recent examples will be reported and the use of these techniques in cases when the three dimensional structure of the target protein is known will be discussed.

Binding Sites↗