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Signaling Pathways

Displaying 265 to 276 (of 537 pathways)

The actin family is a diverse and evolutionarily ancient group of proteins that provide the supportive framework to the three-dimensional structure of eukaryotic cells. It provides the forces that enable the cell to adopt a variety of shapes and to undertake directed movements. Certain cell types, such as polymorphonuclear leukocytes, monocyte/macrophages, and metastatic cells, are able to move rapidly through tissues and these movements are mediated by the actin cytoskeleton (Ref.1). An important property of actin is its ability to produce movement in the absence of motor proteins. At the cell membrane actin microfilament assembly protrudes the membrane forward producing the ruffling membranes in actively moving cells. These microfilaments also play a passive[..]

Ras is a membrane-associated guanine nucleotide-binding protein that is normally activated in response to the binding of extracellular signals, such as growth factors, RTKs (Receptor Tyrosine Kinases), TCR (T-Cell Receptors) and PMA (Phorbol-12 Myristate-13 Acetate). Ras signaling affects many cellular functions, which includes cell proliferation, apoptosis, migration, fate specification, and differentiation. Ras acts as a binary signal switch cycling between ON and OFF states, which are characterized in terms of a small molecule, a guanine nucleotide, bound to the protein. In the resting cell, Ras is tightly bound to GDP (Guanosine Diphosphate), which is exchanged for GTP (Guanosine Triphosphate) upon binding of extracellular stimuli to cell membrane receptors. In the[..]

Complement is a system of circulating enzymes that is part of the body's response to illness or injury. The complement system plays an essential role in host defence against infectious agents and in the inflammatory process. It consists of about thirty plasma proteins that function either as enzymes or as binding proteins. In addition to these plasma proteins, the complement system includes multiple distinct cell-surface receptors that exhibit specificity for the physiological fragments of complement proteins and that occur on inflammatory cells and cells of the immune system. There are also several regulatory membrane proteins that function to prevent autologous complement activation and protect host cells from accidental complement attack. The complement system can[..]

The TNFR (Tumor Necrosis Factor Receptor) superfamily comprises a growing family of type I membrane bound glycoproteins, which interact with the TNF family of soluble mediators and type II transmembrane proteins. At least 23 TNFR superfamily members and 17 known ligands have been identified in mammals. These receptors trigger pleiotropic responses, ranging from apoptosis and differentiation to proliferation, and have been implicated in immune regulation, host defense and lymphoid organ development. Members of the TNFR family are characterized by the presence of varying numbers (two to six) of cysteine-rich repeats in their cytoplasmic domains. Among these molecules, a novel subgroup has been defined, termed DR (Death Receptors), as one of their most prominent functions[..]

GITR (Glucocorticoid-Induced TNFR Family-Related) also termed AITR (Activation-Inducible TNFR Family Receptor) is a member of the TNFRSF18 (TNF Receptor Superfamily 18). It is a 228-amino acids type I transmembrane protein that is suggested to be a close relative of 4-1BB and CD27. Inducible during T-Cell activation, the molecule has a 19 amino acid residue signal sequence, a 134 amino acid residue extracellular region, a 23 amino acid residue transmembrane segment and a 52 amino acid residue cytoplasmic domain. It has three cysteine-rich motifs in its extracellular region. Its ligand is GITRL (AITRL). GITR expression is upregulated on T-Cells. A high level of GITR is constitutively expressed on CD4+ CD25+ regulatory T-Cells. CD4+ GITR+ T-Cells are equivalent to CD4+[..]

The Tubby protein is the founding member of a multigene protein family that plays an important role in maintenance and function of neuronal cells during development and post-differentiation. Currently, four Tubby gene family members (TUB, TULP1, TULP2 and TULP3) have been identified, which are conserved among different species of mammals (Ref.1). Besides, Tubby-like proteins are also found in other multicellular organisms including plants. These proteins feature a characteristic "Tubby domain" of approximately 260 amino acids at the C-terminus that forms a unique helix-filled barrel structure; this C-terminal domain binds avidly to double-stranded DNA. Most Tubby proteins include NH2-terminal regions that, in general, are not closely related to one another.[..]

Development of a functional cardiovascular system is dependent on the regulated proliferation, migration, and differentiation of endothelial cells in two discrete processes known as vasculogenesis and angiogenesis. Angiogenesis is the formation of new capillaries from pre-existing vessels, whereas vasculogenesis is de-novo capillary formation from EPCs (Endothelial Precursor Cells). New capillaries arise from preexisting larger vessels to give rise to a more complex vascular network with a hierarchy of both large and small vessels (Ref.1). These sequential vascular developments are tightly regulated by a range of pro- and antiangiogenic factors, including VEGF (Vascular Endothelial Growth Factor ), bFGF(basic Fibroblast Growth Factor ), Thrombospondin, Angiopoietins,[..]

Actin Nucleation By ARP-WASP Complex For many cell types, the ability to move across a solid surface is fundamental to their biological function. Certain aspects of cell locomotion, such as the protrusion of the plasma membrane in lamellipodia and filopodia, are driven by the polymerization of actin cytoskeleton. The actin cytoskeleton is a dynamic filament network that is essential for cell movement during embryo development, polarization, morphogenesis, cell division, and immune system function and in the metastasis of cancer cells. To engage in these complex behaviors, cells must direct actin assembly with a high degree of spatial and temporal resolution in response to extracellular signals (Ref.1). To coordinate these behaviors, tight spatial and temporal control[..]

Lymphocytes are one of the five kinds of white blood cells or leukocytes, circulating in the blood. Although mature lymphocytes all look pretty much alike, they are extraordinarily diverse in their functions. The most abundant lymphocytes are: B-Lymphocytes (often simply called B-Cells) and T-Lymphocytes (likewise called T-Cells) [Ref.1]. B-Cells are not only produced in the bone marrow but also mature there. Each B-Cell is specific for a particular antigen. The specificity of binding resides in the BCR (B-Cell receptor) for antigen [Ref.2]. Mature B cells express two BCR isotypes, IgM and IgD. The BCR is composed of mIg (membrane immunoglobulin); a structure of four (in the case of IgD) or five (IgM) immunoglobulin domains in the heavy chain linked by a hinge, and a[..]

The SM (Sphingomyelin) pathway is an evolutionarily conserved stress response system linking diverse environmental stresses (Ultraviolet, Heat Shock, Oxidative Stress, and Ionizing Radiation) to cellular effector pathways. Ceramide is the second messenger in this system and can be generated either by hydrolysis of SM through SM-specific PLC (Phospholipase-C) termed SMases (Sphingomyelinases) or by de novo synthesis through the enzyme Ceramide Synthase . There are two classes of SMase, acidic (A-Smase) and neutral (N-Smase). Stress stimuli such as, TNF-Alpha (Tumor Necrosis Factor-Alpha), lipopolysaccharide, and some chemotherapy drugs such as doxorubicin also mediate apoptosis by generation of the lipid second messenger, Ceramide. A specific interaction between the FAN[..]

The ability of multicellular organisms to maintain cellular homeostasis is critically dependent on a balance between cell survival and cell death (apoptosis). The responsiveness of individual cells to death signals varies greatly depending on the presence of continuous survival cues from the extracellular environment. The perturbation of normal cell survival mechanisms, leading to an increase in cell survival or cell death plays an important role in the development of a number of disease states, including cancer. BAD (BCL2 Associated Death Promoter) is a pro-apoptotic critical regulatory component of the intrinsic cell death machinery that exerts its death-promoting effect upon heterodimerization with the antiapoptotic proteins of the BCL2 family defined by conserved[..]

TGFB (Transforming growth factor-beta) is a multifunctional cytokine that regulates a wide variety of cellular functions, including cell growth, cellular differentiation, apoptosis, and wound healing. TGF-b signals are transmitted through two transmembrane serine/threonine kinase receptors TGFBR1 and TGFBR2 [Ref.1]. Initiation of the TGFB signaling cascade occurs upon ligand binding to TGFB receptor TGFBR2 and subsequent TGFBR1– TGFBR2 heterotetrameric complex formation. TGFBR2 is a constitutively active receptor kinase and phosphorylates Ser/Thr residues in the cytoplasmic GS domain of TGFBR1, which turns on the kinase activity of TGFBR1. Upon Activation, TGFBR1 transmits its signal to the various intracellular SMAD-dependent and SMAD independent signaling[..]

Displaying 265 to 276 (of 537 pathways)


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