Cell Bio 11.11.09 -DNA anti parallel double helix 3´and 5´ end between the strands hydrogen bonds major groove and minor groove spherical hindrance makes other parings impossible circular molecule in bacteria chloroplasts mitochondria several viruses problems when denatured or during replication · tension in the rest · when opened at the middle extra twist tighter bindings to the bindings right and left · super-coiling (telephone) · structure → super-coil simian virus 40 → double stranded DNA virus, infects monkeys…
Cloning: Definition, types and stemm cell research Table of contents: Definiton of clones 3 types of cloning Stem cell research , Definition of Stem cells, iPS cells Vocab What are clones? -Clones are defined by having identical genetic material. That means their sequence of bases in their DNA is exactly the same. A DNA consists out of 4 bases. Twins are an example for being clones, because they do have exactly the same DNA. Another example is a Bacterium. It can clone/ replicate himself and is used in science. The 3 types of cloning: It is…
T cell ion channels and their role for activation
T-Zell Aktivierung und die Rolle von Ionenkanälen
T cell ion channels and their role for T cell activation
1.) T cells
As well as B-cells and natural killer cells (NK), T cells belong to the lymphocytes and present a hallmark of the adaptive immunity in vertebrates. All T cells originate from a progenitor cell in the bone narrow and undergo maturation in the thymus. During maturation the T lymphocytes are being provided with different membrane-bound receptors and cell surface markers distinguishing distinct T cell subsets with unique functions.
T cell subsets: Depending on the composition of their T cell antigen receptor (TCR) the T cells are subdivided into αβ-T cells and γδ-T cells. Αβ-T cells account for the biggest part of the T cells with around 90-95% and represent about 70% of all peripheral blood mononuclear cells (PBMC). They circulate continuously from the bloodstream to the lymphatic system and lymphoid organs back to the blood, making contact with antigen presenting cells (APCs).
The most important factor for the recognition of different antigens is the T cell receptor (TCR). The α- and β-chains of the heterodimeric TCR are composed of a variable and a constant region, which during maturation are spliced together into a single type of functional αβ-TCR which d.....[read full text]
According to the two-signal-hypothesis naïve T cells also require a second, co-stimulatory signal to be fully activated. This signal can be provided by co-stimulatory receptors of which the most commonly described one is CD28. Binding of CD28 to its ligand CD80/CD86 (B7.1/B7.2) expressed on activated APCs leads to downstream signaling critical for T cell activation (Chen & Flies 2013).
Signaling pathways: Three main pathways lead to T cell activation after TCR triggering. The first step in the signaling cascade of T cell activation is the phosphorylation of the CD3 ITAMs by the co-receptor-associated Lck kinase leading to recruitment of further signaling complexes and results in the activation of phospholipase Cγ1 (PLCγ1), which is the initiator for important downstream pathway.....
CRAC channels are negatively regulated by Ca2+ ions and are very susceptible to membrane potential changes (Zweifach 1995; Zweifach & Lewis 1995).Depolarization decreases Ca2+ entry whereas hyperpolarization increases Ca2+ entry through CRACchannels. Therefore, CRAC channels alone cannot enable prolonged Ca2+ influx necessary for T cell activation, making K+ channels also important players in the activation process.
Potassium channels: The Kv1.3 channel is activated at membrane potentials depolarized over -60mV, leading to a K+ outward current along the electrochemical gradient hyperpolarizing the membrane potential (Cahalan et al. 1985). Inactivation of Kv1.3 follows sustained depolarization of the membrane potential due to conformational changes (Panyi et al. 1995). Another important potassium channel is KCa3.1 activated by Ca2+ conce.....
Zweifach, A. & Lewis, R.S., 1993. Mitogen-regulated Ca2+ current of T lymphocytes is activated by depletion of intracellular Ca2+ stores. Proceedings of the National Academy of Sciences, 90(13), pp.6295–6299.
Zweifach, A. & Lewis, R.S., 1995. Slow calcium-dependent inactivation of depletion-activated calcium current. Store-dependent and -independent mechanisms. The Journal of biological chemistry, .....