Neil A. Clipstone

Bio: Neil A. Clipstone is an academic researcher from Northwestern University. The author has contributed to research in topics: Calcineurin & Signal transduction. The author has an hindex of 20, co-authored 21 publications receiving 5924 citations. Previous affiliations of Neil A. Clipstone include Loyola University Chicago & Stanford University.

Identification of calcineurin as a key signalling enzyme in T-lymphocyte activation

Abstract: THE immunosuppressive drugs cyclosporin A (CsA) and FKS06 both interfere with a Ca2+-sensitive T-cell signal transduction pathway1–4thereby preventing the activation of specific transcription factors (such as NF-AT and NF-IL2A)1,5–7involved in lymphokine gene expression. CsA and FK506 seem to act by interaction with their cognate intracellular receptors8–10, cyclophilin and FKBP, respectively (see ref. 11 for review). The Ca2+/calmodulin-regulated phosphatase calcineurin is a major target of drug-isomerase complexes in vitro12We have therefore tested the hypothesis that this interaction is responsible for the in vivo effects of CsA/FK506. We report here that overexpression of calcineurin in Jurkat cells renders them more resistant to the effects of CsA and FK506 and augments both NFAT- and NFIL2A-dependent transcription. These results identify calcineurin as a key enzyme in the T-cell signal transduction cascade and provide biological evidence to support the notion that the interaction of drug-isomerase complexes with calcineurin underlies the molecular basis of CsA/FK506-mediated immunosuppression.

Signal transmission between the plasma membrane and nucleus of t lymphocytes

Abstract: INITIATING THE GENETIC PROGRAM LEADING TO T CELL ACTIVATION 1057 Integration of the Diverse Signals Required for T Cell Activation on the Regulatory Regions of Early Genes ..... .. . .. . .. . . ... . 1057 The NF-AT Transcriptional Complex . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1058 An Association Between JUIl D and Octl Appears to Play an Important Role ill Activating the IL-2 Gene ....... . .... .... ..... . .. . . 1062 The Roles of NF-Kl3 and AP-l in T Cell Activation . . . . . ... . . . .. .. . . . 1063 CALCINEURIN: AN ESSENTIAL SIGNALLING INTERMEDIATE ......... 1064 Calcineurin in Other Cells and Species .. . ...... . .. . 1069 Is Calcineurin a Rate-Limiting Step in T Cell Activation? 1070

Rapid shuttling of NF-AT in discrimination of Ca2+ signals and immunosuppression.

Abstract: Cells need to distinguish between transient Ca2+ signals that induce events such as muscle contraction, secretion, adhesion and synaptic transmission, and sustained Ca2+ signals that are involved in cell proliferation and differentiation. The latter class of events is blocked in lymphocytes by the immunosuppressive drugs cyclosporin A and FK506, which inhibit calcineurin, a Ca2+-activated serine/threonine phosphatase necessary for the nuclear import of NF-AT transcription factors. Here we report that sustained high concentrations of Ca2+, but not transient pulses, are required to maintain NF-AT transcription factors in the nucleus, where they participate in Ca2+-dependent induction of genes required for lymphocyte activation and proliferation. Furthermore, overexpression and constitutive nuclear localization of NF-AT, but not Jun, Fos, NF-kappaB, Oct or Ets family members, renders the interleukin-2 enhancer in Jurkat T lymphocytes resistant to FK506 and cyclosporin A. Thus a primary effect of these immunosuppressive reagents is to control the subcellular localization of the NF-AT family of transcription factors.

Nuclear localization of NF-ATc by a calcineurin-dependent, cyclosporin-sensitive intramolecular interaction.

Abstract: The NF-AT family of transcription factors participates in the regulation of early immune response genes such as IL-2, IL-4, CD40 ligand, and Fas ligand in response to Ca2+/calcineurin signals initiated at the antigen receptor. Calcineurin activation leads to the rapid translocation of NF-AT family members from cytoplasm to nucleus, an event that is blocked by the immunosuppressive drugs cyclosporin A and FK506. We show that translocation requires two redundant nuclear localization sequences and that one sequence is in an intramolecular association with phosphorserines in a conserved motif located at the amino terminus of each NF-AT protein. Mutation of serines in this motif in NF-ATc both disrupts this intramolecular interaction and leads to nuclear localization, suggesting a model of NF-AT nuclear import in which dephosphorylation by calcineurin causes exposure of two nuclear localization sequences.

The versatility and universality of calcium signalling

Abstract: The universality of calcium as an intracellular messenger depends on its enormous versatility. Cells have a calcium signalling toolkit with many components that can be mixed and matched to create a wide range of spatial and temporal signals. This versatility is exploited to control processes as diverse as fertilization, proliferation, development, learning and memory, contraction and secretion, and must be accomplished within the context of calcium being highly toxic. Exceeding its normal spatial and temporal boundaries can result in cell death through both necrosis and apoptosis.

Mammalian Mitogen-Activated Protein Kinase Signal Transduction Pathways Activated by Stress and Inflammation

Abstract: The molecular details of mammalian stress-activated signal transduction pathways have only begun to be dissected. This, despite the fact that the impact of these pathways on the pathology of chroni...

The Immunological Synapse: A Molecular Machine Controlling T Cell Activation

Abstract: The specialized junction between a T lymphocyte and an antigen-presenting cell, the immunological synapse, consists of a central cluster of T cell receptors surrounded by a ring of adhesion molecules. Immunological synapse formation is now shown to be an active and dynamic mechanism that allows T cells to distinguish potential antigenic ligands. Initially, T cell receptor ligands were engaged in an outermost ring of the nascent synapse. Transport of these complexes into the central cluster was dependent on T cell receptor—ligand interaction kinetics. Finally, formation of a stable central cluster at the heart of the synapse was a determinative event for T cell proliferation. A critical event in the initiation of the adaptive

TRANSCRIPTION FACTORS OF THE NFAT FAMILY:Regulation and Function

Abstract: As targets for the immunosuppressive drugs cyclosporin A and FK506, transcription factors of the NFAT (nuclear factor of activated T cells) family have been the focus of much attention. NFAT proteins, which are expressed in most immune-system cells, play a pivotal role in the transcription of cytokine genes and other genes critical for the immune response. The activity of NFAT proteins is tightly regulated by the calcium/calmodulin-dependent phosphatase calcineurin, a primary target for inhibition by cyclosporin A and FK506. Calcineurin controls the translocation of NFAT proteins from the cytoplasm to the nucleus of activated cells by interacting with an N-terminal regulatory domain conserved in the NFAT family. The DNA-binding domains of NFAT proteins resemble those of Rel-family proteins, and Rel and NFAT proteins show some overlap in their ability to bind to certain regulatory elements in cytokine genes. NFAT is also notable for its ability to bind cooperatively with transcription factors of the AP-1 (Fos/Jun) family to composite NFAT:AP-1 sites, found in the regulatory regions of many genes that are inducibly transcribed by immune-system cells. This review discusses recent data on the diversity of the NFAT family of transcription factors, the regulation of NFAT proteins within cells, and the cooperation of NFAT proteins with other transcription factors to regulate the expression of inducible genes.