General Signaling Principles
Characteristics of a signal/change: – Perturbation from steady state – Reproducible – Managed – Controlled Stimulus Steroid hormones are allophonic and can therefore defuse across plasma membranes; hey form signaling complexes with proteins A signal binds a surface receptor ( induction of conformational change In the Intracellular domain of the receptor ( transduction and amplification of the signal Vela downstream partners either linear or via network upon induction cells can start making signaling molecules that work either in an autocratic (same cell (type)) fashion or in a appearance (other cells) fashion.
Adhesion molecules can also Induce signaling; whether a cell Is attached or not. Signaling requires: – Coordination – Control in space Control of time ( Spatial and temporal control): o When? O Where? O For how long? Position – concentration – duration – sequence Examples of stimuli: hormones, neurotransmitters, ions, lipids, SGF, deodorants, cytokines, photons, other cells etc…
Cells can sense damage in nearby tissue for example by the release of ADAPT from injured cells Examples for signaling molecules: Neurotransmitters: Acetylene’s Hormones: AAA, peptides, fatty acids cytokines: TNT alpha (xx AAA, kid) TGIF beta 400 AAA GM-SF Receptors There is no pattern among signals, is there one among receptors?
Different receptor types: – Ion channels (voltage and aligned dependent, intracellular downstream) receptors (membrane spanning proteins) – Electioneering/lissomness: growth factors – 7-TM – Intracellular: steroid receptors, nuclear receptors, transcription factors Good Receptors are extremely sensitive: The physiological response curve is left (black line) to the occupied receptor curve (green curve), implying that a lot of receptors are still unoccupied while signaling is occurring. However, this is enough to result in an enormous response.
A typical concentration for a signal molecule is 10-10 M ( 6×1013 hormone particles/ liter Cell diameter is about 12 pm ( 60 hormone particles per cell is enough to induce signaling Good news (2): Many receptors have similar structures Example: 7-transmigrate spanning receptors (7-TM receptors) ( 1000 genes out of 25000 genes ( makes 4% of molecules which have similarities with the 7-TM receptor Bad news: Similar receptors can have different mechanisms and downstream signaling, this makes them very complex to study.