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Angaben zur Quelle [Bearbeiten]

Autor     Andrew J. Hapel, E. Richard Stanley
Titel    Cytokines, Receptors and Signalling Pathways Involved in Macrophage and Dendritic Cell Development
Sammlung    Madame Curie Report
Herausgeber    Jonathan Keller
Verlag    Landes Bioscience
Jahr    2006
Seiten    17
URL    http://www.landesbioscience.com/pdf/HapelReport.pdf

Literaturverz.   

no
Fußnoten    no
Fragmente    4


Fragmente der Quelle:
[1.] Pak/Fragment 017 09 - Diskussion
Zuletzt bearbeitet: 2014-04-06 06:49:29 Hindemith
Fragment, Gesichtet, Hapel and Stanley 2006, KomplettPlagiat, Pak, SMWFragment, Schutzlevel sysop

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Cytokines exert their action through high-affinity receptors on the cell surface that are linked to pathways of cellular activation, commitment, differentiation, survival, proliferation and differentiation.

Cross-linking of receptor subunits on the outside of the cell wall leads to adjoining of kinases associated with the intracellular receptor tails, either as intrinsic activities, or because of pre-association of secondary kinase molecules. This intracellular association of signaling molecules results in phosphorylation of tyrosine residues in the receptor tail and binding of further signaling molecules that have phospho-tyrosine-binding domains. Several aspects of the downstream intracellular pathways of cytokines are similar, because different activated receptor cytoplasmic domains often bind a common signaling molecule or family of signaling molecules. Thus stoichiometry and rate of reaction are important regulatory influences that allow discrimination between signaling processes with different outcomes (Molecular cell biology. Lodish, Harvey F. 5. ed. )

1.3.2. Cooperative Interaction of Cytokines

For efficient in vitro proliferation and differentiation, pluripotent and multipotent progenitor cells require a combination of cytokines [e.g. SCF, IL-1, IL-3, IL-6, GM-CSF, and colony stimulating factor-1, (CSF-1)]. Immature haematopoietic cells have been shown to co-express a number of different lineage specific receptors at low levels. As these immature cells develop, they lose receptors for [some cytokines e.g. SCF and IL-3, while retaining receptors for later acting cytokines such as CSF-1.]

Cytokines exert their action through high-affinity receptors on the cell surface that are linked to pathways of cellular activation, survival, proliferation and differentiation. Cross-linking of receptor subunits on the outside of the cell wall leads to abutting of kinases associated with the intracellular receptor tails, either as intrinsic activities, or because of pre-association of secondary kinase molecules. This intracellular association of signalling molecules results in phosphorylation of tyrosine residues in the receptor tail and binding of further signalling molecules that have phospho-tyrosine-binding domains. Several aspects of the downstream intracellular pathways of cytokines are similar, because different activated receptor cytoplasmic domains often bind a common signalling molecule or family of signalling molecules. Thus stoichiometry and rate of reaction are important regulatory influences that allow discrimination between signalling processes with different outcomes.

Cooperative Interaction of Cytokines in Proliferation and Differentiation

For efficient in vitro proliferation and differentiation, PPSCs and multi-potent progenitor cells require a combination of cytokines. (e.g., SCF, IL-1, IL-3, IL-6, GM-CSF, and CSF-1).23,24 As might be expected from this observation, immature haematopoietic cells have been shown to co-express a number of different lineage specific receptors at low levels.25 As these immature cells develop, they lose receptors for some cytokines e.g., SCF and IL-3, while retaining receptors for later acting cytokines such as CSF-1.


23. Bradley TR, Hodgson GS. Detection of primitive macrophage progenitor cells in mouse bone marrow. Blood 1979; 54:1446–1450.

24. Stanley ER, Bartocci A, Patinkin D et al. Regulation of very primitive multipotent haematopoietic cells by Hemopoietin–1. Cell 1986; 45:667–674.

25. Cross MA, Enver T. The lineage commitment of haematopoietic progenitor cells. Curr Opin Genet Devel 1997; 7:609-613.

Anmerkungen

Identical, without any part of it marked as a citation.

Pak names a general source, but this passage is not to be found there.

Sichter
(Graf Isolan) Singulus

[2.] Pak/Fragment 018 01 - Diskussion
Zuletzt bearbeitet: 2014-04-06 07:31:02 Hindemith
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[As these immature cells develop, they lose receptors for] some cytokines e.g. SCF and IL-3, while retaining receptors for later acting cytokines such as CSF-1.

Eventually immature cells reach the stage of the committed progenitor cell, where their proliferation and differentiation are along one particular lineage, guided by the lineage-restricted cytokines. Synergy occurs between some late-acting lineages restricted cytokines such as CSF-1, EPO and G-CSF, with early acting cytokines such as SCF and IL-3, in stimulating the proliferation and differentiation of multi-potent cells. This provides a mechanism by which the tightly regulated changes in the level of a late acting cytokine can be coupled to the channelling of multi-potent progenitor cells into a lineage to satisfy the demand for differentiated cells. The underlying mechanism of synergy may lie at the level of either the receptors or at the level of post receptor signaling pathways (Molecular cell biology. Lodish, Harvey F. 5. ed. )

[Page 2]

As these immature cells develop, they lose receptors for some cytokines e.g., SCF and IL-3, while retaining receptors for later acting cytokines such as CSF-1. Eventually at least some of the immature cells reach the stage of committed progenitor cell, where their further proliferation and differentiation are along one particular lineage, dictated by the relevant lineage-restricted cytokine.

[Page 3]

Synergy occurs between some late-acting lineage restricted cytokines such as CSF-1, EPO and G-CSF, with early acting cytokines such as SCF and IL-3, in stimulating the proliferation and differentiation of multi-potent cells. This provides a mechanism by which the tightly regulated changes in the level of a late acting cytokine, can be coupled to the channelling of multi-potent progenitor cells into a lineage to satisfy the demand for differentiated cells. The underlying mechanism of synergy may lie at the level of either the receptors or at the level of post receptor signalling pathways.

Anmerkungen

Identical, without any part of it marked as a citation.

Pak names a standard textbook as a general source (which cannot be found in her list of references), but this passage is not to be found there.

Sichter
(Graf Isolan) Singulus

[3.] Pak/Fragment 019 04 - Diskussion
Zuletzt bearbeitet: 2014-04-06 09:11:05 Hindemith
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1.3.3. Tyrosine kinase receptor and cell signalling

Many cytokines such as CSF-1, SCF and FL are homodimeric that share some sequence homology and are structurally similar to one another. These three cytokines/ growth factors have complex patterns of expression due to alternative mRNA splicing. This allows them to be expressed as either membrane-spanning, cell-surface or secreted glycoproteins. All three growth factors are widely expressed in all tissues and two of them, SCF and CSF-1, also affect non-haematopoietic as well as haematopoietic cells.

The receptors for the above cytokines are members of the platelet derived growth factor (PDGF) receptor family. Each receptor possesses an extra-cellular domain, consisting of a five immunoglobulin (Ig) like repeat. These repeats are: a heavily glycosylated with N-linked sugars, a trans-membrane domain, intra-cellular domains containing a juxta-membrane region, a src-related tyrosine kinase domain that is interrupted by a kinase insert domain, and a carboxy-terminal tail. The three amino terminal Ig-like domains incorporate the ligand binding domains of the SCF and CSF-1 receptors. Binding of this type of dimeric receptor to its cognate ligand stabilizes the non-covalent association between the two chains of the receptor at the cell surface and permits the trans-phosphorylation of the intra-cellular domain of one chain by the other.

Tyrosine phosphorylation in response to cytokine binding is not restricted to those proteins that are stably associated with the receptor. Regions containing tyrosines that are phosphorylated as a consequence of receptor activation act as docking sites for src-homology region 2 (SH2) domains of signaling and adaptor proteins. These proteins in turn may interact with plasma membrane associated proteins. An example is the association of recruited Grb2/Sos with Ras, which leads to their activation. The associated proteins may themselves become tyrosine phosphorylated.

Tyrosine Kinase Receptors

CSF-1, SCF and FL are homodimeric cytokines that share some sequence homology and structurally are similar to one another.36-40 All three cytokines have complex patterns of expression due to alternative mRNA splicing. This allows them to be expressed as either membrane-spanning, cell-surface or secreted glycoproteins. All three growth factors are widely expressed in all tissues and at least two of them, SCF and CSF-1, affect non-haematopoietic as well as haematopoietic cells.

The receptors for the above cytokines are members of the PDGF receptor family.39-42 Each receptor possesses an extra-cellular domain comprising five Ig-like repeats which are heavily glycosylated with N-linked sugars, a trans-membrane domain, and intra-cellular domains containing a juxta-membrane region, a src-related tyrosine kinase domain that is interrupted by a kinase insert domain, and a carboxy-terminal tail. The three amino terminal Ig-like domains incorporate the ligand binding domains of the SCF and CSF-1 receptors.

Binding of this type of dimeric receptor to its cognate ligand stabilises the non-covalent association between the two chains of the receptor at the cell surface and permits the trans-phosphorylation of the intra-cellular domain of one chain by the other.

Tyrosine phosphorylation in response to cytokine binding is not restricted to those proteins that are stably associated with the receptor. Regions containing tyrosines that are phosphorylated as a consequence of receptor activation act as docking sites for src homology region 2 (SH2) domains of signalling and adaptor proteins. These proteins in turn may interact with plasma membrane associated proteins. An example is the association of recruited Grb2/Sos with Ras, which leads to their activation. Or the associated proteins may themselves become tyrosine phosphorylated.


36. Anderson DM, Williams DE, Tushinski R et al. Alternate splicing of mRNA encoding human mast cell growth factor and localisation of the gene to chromosome 12q22-24. Cell Growth Differ 1991; 2:373-378.

37. Bazan JF. Genetic and structural homology of stem cell factor and macrophage colony stimulating factor. Cell 1991; 65:9-10.

38. Flanagan JG, Chan DC, Leder P. Transmembrane form of the kit ligand growth factor is determined by alternative splicing and is missing in the Sld mutant. Cell 1991; 64:1025-1035.

39. Lyman SD, Jacobsen SEW. c-kit ligand and flt-3 ligand : stem cell factors with overlapping yet distinct activities. Blood 1998; 91:1101–1134.

40. Stanley ER. CSF-1. In: Oppenheim JJ, Feldmann M, eds. Cytokine Database. London: Academic 2000:913–934.

41. Qui F, Ray P, Brown K et al. Primary structure of c-kit: relationship with the CSF1/PDGF receptor kinase family - oncogenic activation of v-kit involves deletion of extracellular domain and C terminus. EMBO J 1988; 7:1003-1011.

42. Coussens L, van Beveren C, Smith D et al. Structural alteration of viral homologue of receptor proto oncogene fms at carboxy-terminus. Nature 1986; 32:277-280.

Anmerkungen

A literal copy except for minute details, without any part of it marked as a citation. No source given.

Sichter
(Graf Isolan) Agrippina1

[4.] Pak/Fragment 020 01 - Diskussion
Zuletzt bearbeitet: 2014-04-06 07:32:31 Hindemith
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[Many of the signaling pathways activated by SCF, CSF] 1 and flat-3 ligand (FL) receptors, including the Ras/Raf-mitogen activated protein kinase cascade, the janus kinase (JAK)/ signal transducers and activators of transcription (STATs) pathway, Src family members and phosphatidylinositol-3-kinase (PI3K), are shared.

All three receptors are likely to exhibit ligand induced, Cbl-mediated decreases in receptor expression. The SCF and CSF-1 receptors are encoded by the proto-oncogenes c-kit and c-fms, respectively. The oncogenes derived from these two proto-oncogenes are present in mutated forms in retroviruses that cause sarcoma in cats. The mutations in the receptor genes cause constitutive activation of the receptors in the absence of cytokines, thus contributing to unregulated cell proliferation.

1.3.4. The role of transcription factors

Nuclear transcription factors are essential for stem cell lineage commitment.

[Page 3]

The Role of Transcription Factors

Experiments using gene manipulation have shown that nuclear transcription factors are essential for stem cell lineage commitment.

[Page 4]

Many of the signalling pathways activated by SCF, CSF-1 and FL receptors, including the Ras/Raf-mitogen activated protein kinase cascade, the Janus kinase (JAK) signal transducers and activation of transcription (STAT) pathway, Src family members and phosphatidylinositol-3-kinase (PI3K), are shared.43 All three receptors are likely to exhibit ligand induced, Cbl-mediated decreases in receptor expression.44

The SCF and CSF-1 receptors are encoded by the proto-oncogenes c-kit and c-fms respectively.45 The oncogenes derived from these two proto-oncogenes are present in mutated forms in retroviruses that cause sarcoma in cats. The mutations in the receptor genes cause constitutive activation of the receptors in the absence of cytokines.45 thus contributing to unregulated cell proliferation.


43. Linnekin D. Early signalling pathways activated by c-Kit in haemopoietic cells. Int J Biochem Cel Biol 1999; 31:1053-1074.

44. Lee PS, Wang Y, Dominguez MG et al. The Cbl protooncoprotein stimulates CSF-1 receptor multiubiquitination and endocytosis, and attenuates macrophage proliferation. EMBO J 1999; 18:3616-3628.

45. Sherr CJ. Colony Stimulating Factor 1 Receptor. Blood 1990; 75:1-1.

Anmerkungen

Identical, without any part of it marked as a citation. No source given.

Sichter
(Graf Isolan) Agrippina1

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