Biomedical subjects

Futoshi Suizu

Publications and source records attributed to Futoshi Suizu.

6 recordsLinked to original sources

PubMed2006

Identification of nerve growth factor-responsive element of the TCL1 promoter as a novel negative regulatory element.

The serine/threonine kinase, Akt (protein kinase B) plays a central role in the regulation of intracellular cell survival. Recently, we demonstrated that the proto-oncogene TCL1, overexpressed in human T-cell prolymphocytic leukemia, is an Akt kinase co-activator. Tightly restricted TCL1 gene expression in early developmental cells suggested that the TCL1 gene is regulated at a transcriptional level. To characterize how TCL1 gene expression is regulated, we cloned the 5'-promoter of the TCL1 gene located at human chromosome 14q32. The 5'-TCL1 promoter region contains a TATA box with cis-regulatory elements for Nur77/NGFI-B (nerve growth factor-responsive element (NBRE), CCAAGGTCA), NFkappaB, and fork head transcription factor. Nur77/NGFI-B, an orphan receptor superfamily transcription factor implicated in T-cell apoptosis, is a substrate for Akt. We hypothesized that TCL1 transactivity is regulated through Akt-induced phosphorylation of Nur77/NGFI-B in vivo. In an electrophoretic mobility shift assay with chromosomal immunoprecipitation assays, wild-type Nur77, but not S350A mutant Nur77, could specifically bind to TCL1-NBRE. A luciferase assay demonstrated that TCL1-NBRE is required for inhibition of TCL1 transactivity upon nerve growth factor/platelet-derived growth factor stimulation, which activates Akt and phosphorylates Nur77. Using a chromosomal immunoprecipitation assay with reverse transcription-PCR, nerve growth factor stimulation inhibited binding of endogenous Nur77 to TCL1-NBRE, in turn, suppressing TCL1 gene expression. The results together establish that TCL1-NBRE is a novel negative regulatory element of Nur77 (NGFI-B). To the best of our knowledge, TCL1-NBRE is the first direct target of Nur77 involving the regulation of intracellular cell death survival. This Akt-induced inhibitory mechanism of TCL1 should play an important role in immunological and/or neuronal development in vivo.

Animals↗

PubMed2006

Targeting carcinogenesis: a role for the prolyl isomerase Pin1?

Phosphorylation of proteins on serine or threonine residues that immediately precede proline (pSer/Thr-Pro) is a central signaling mechanism in cell proliferation and transformation. Recent studies indicate that certain pSer/Thr-Pro motifs in native proteins exist in two completely distinct conformations, cis and trans, whose conversion is markedly slowed down upon phosphorylation, but specifically catalyzed by the peptidyl-prolyl cis/trans isomerase Pin1. Importantly, such Pin1-catalyzed conformational changes can have profound effects on the function of many phosphorylation signaling pathways, thereby playing an important role in various cellular processes. Moreover, increasing evidence indicates that aberrant Pin1 function plays an important role in the pathogenesis of some human diseases. Notably, Pin1 is not only overexpressed in a large number of human cancers, but also is an excellent prognostic marker in some cancers. Furthermore, Pin1 overexpression can function as a critical catalyst that amplifies multiple oncogenic signaling pathways during oncogenesis. Moreover, Pin1 overexpression causes cell transformation, centrosome amplification, genomic instability, and tumor development. In contrast, Pin1 knockout in mice prevents certain oncogenes from inducing tumors and Pin1 inhibition in cancer cells suppresses their cell proliferation, transformed phenotype and tumorigenicity in nude mice as well as increases the response to other anticancer agents. These results suggest that Pin1-mediated postphosphorylation regulation may provide a unique opportunity for disrupting oncogenic pathways, and thereby represent an appealing target for novel anticancer therapies.

Catalysis↗

PubMed2006

Pin1 regulates centrosome duplication, and its overexpression induces centrosome amplification, chromosome instability, and oncogenesis.

Phosphorylation on Ser/Thr-Pro motifs is a major mechanism regulating many events involved in cell proliferation and transformation, including centrosome duplication, whose defects have been implicated in oncogenesis. Certain phosphorylated Ser/Thr-Pro motifs can exist in two distinct conformations whose conversion in certain proteins is catalyzed specifically by the prolyl isomerase Pin1. Pin1 is prevalently overexpressed in human cancers and is important for the activation of multiple oncogenic pathways, and its deletion suppresses the ability of certain oncogenes to induce cancer in mice. However, little is known about the role of Pin1 in centrosome duplication and the significance of Pin1 overexpression in cancer development in vivo. Here we show that Pin1 overexpression correlates with centrosome amplification in human breast cancer tissues. Furthermore, Pin1 localizes to and copurifies with centrosomes in interphase but not mitotic cells. Moreover, Pin1 ablation in mouse embryonic fibroblasts drastically delays centrosome duplication without affecting DNA synthesis and Pin1 inhibition also suppresses centrosome amplification in S-arrested CHO cells. In contrast, overexpression of Pin1 drives centrosome duplication and accumulation, resulting in chromosome missegregation, aneuploidy, and transformation in nontransformed NIH 3T3 cells. More importantly, transgenic overexpression of Pin1 in mouse mammary glands also potently induces centrosome amplification, eventually leading to mammary hyperplasia and malignant mammary tumors with overamplified centrosomes. These results demonstrate for the first time that the phosphorylation-specific isomerase Pin1 regulates centrosome duplication and its deregulation can induce centrosome amplification, chromosome instability, and oncogenesis.

Amino Acid Motifs↗

PubMed2005

Phosphorylation-specific prolyl isomerization: is there an underlying theme?

The prolyl isomerase Pin1 is a conserved enzyme that is intimately involved in diverse biological processes and pathological conditions such as cancer and Alzheimer's disease. By catalysing cis-trans interconversion of certain motifs containing phosphorylated serine or threonine residues followed by a proline residue (pSer/Thr-Pro), Pin1 can have profound effects on phosphorylation signalling. The structural and functional differences that result from cis-trans isomerization of specific pSer/Thr-Pro motifs probably underlie most, if not all, Pin1-dependent actions. Phosphorylation-dependent prolyl isomerization by Pin1 remains a unique mode for the modulation of signal transduction. Here, we provide an overview of the plethora of regulatory events that involve this unique enzyme, with a particular focus on oncogenic signalling and neurodegeneration.

Alzheimer Disease↗

PubMed2003

Regulation of NF-kappaB signaling by Pin1-dependent prolyl isomerization and ubiquitin-mediated proteolysis of p65/RelA.

The transcription factor NF-kappaB is activated by the degradation of its inhibitor IkappaBalpha, resulting in its nuclear translocation. However, the mechanism by which nuclear NF-kappaB is subsequently regulated is not clear. Here we demonstrate that NF-kappaB function is regulated by Pin1-mediated prolyl isomerization and ubiquitin-mediated proteolysis of its p65/RelA subunit. Upon cytokine treatment, Pin1 binds to the pThr254-Pro motif in p65 and inhibits p65 binding to IkappaBalpha, resulting in increased nuclear accumulation and protein stability of p65 and enhanced NF-kappaB activity. Significantly, Pin1-deficient mice and cells are refractory to NF-kappaB activation by cytokine signals. Moreover, the stability of p65 is controlled by ubiquitin-mediated proteolysis, facilitated by a cytokine signal inhibitor, SOCS-1, acting as a ubiquitin ligase. These findings uncover two important mechanisms of regulating NF-kappaB signaling and offer new insight into the pathogenesis and treatment of some human diseases such as cancers.

Amino Acid Motifs↗

PubMed2002

Characterization of Ca2+/calmodulin-dependent protein kinase I as a myosin II regulatory light chain kinase in vitro and in vivo.

Ca(2+)/calmodulin (CaM)-dependent protein kinase I (CaM-KI), which is a member of the multifunctional CaM-K family, is thought to be involved in various Ca(2+)-signalling pathways. In this report, we demonstrate that CaM-KI activated by an upstream kinase (CaM-K kinase), but not unactivated CaM-KI, phosphorylates myosin II regulatory light chain (MRLC) efficiently ( K (cat), 1.7 s(-1)) and stoichiometrically (approximately 0.8 mol of phosphate/mol) in a Ca(2+)/CaM-dependent manner in vitro. One-dimensional phosphopeptide mapping and mutational analysis of MRLC revealed that the activated CaM-KI monophosphorylates only Ser-19 in MRLC. Transient expression of the Ca(2+)/CaM-independent form of CaM-KI (CaM-KI(1-293)) in HeLa cells induced Ser-19 phosphorylation of myosin, II accompanied by reorganization of actin filaments in the peripheral region of the cells. CaM-KI-induced reorganization of actin filaments was suppressed by co-expression of non-phosphorylatable MRLC mutants (S19A and T18AS19A). Furthermore, a kinase-negative form of CaM-KI (CaM-KI(1-293,K49E)) significantly reduced reorganization of actin filaments, indicating a dominant negative effect. This is the first demonstration that the activation of the CaM-KI cascade induces myosin II phosphorylation, resulting in regulation of actin filament organization in mammalian cells.

Actin Cytoskeleton↗