Signalling Transduction

 

Signal Transduction

• summary

  In signal transduction, extracellular signals are converted into intracellular signals: A signaling molecule (ligand) reaches its target cell and binds to a specific receptor. This activates a signaling cascade involving intracellular enzymes and molecules (second messengers), which again leads to a specific reaction. Via signal amplification, the number of signaling molecules is increased at every step of the signal cascade.

  

• terminology

  • Receptor
  • Ligand (first messenger):
  • Second messenger
  • Signaling cascade
  • Signal amplification

  

  

Receptors

• overview

  Extracellular messengers have to bind to a receptor to exert their effect. Lipophilic messengers can pass through the cell membrane and bind to intracellular receptors, while hydrophilic messengers cannot due to the lipophilic properties of the cell membrane. Therefore, hydrophilic messengers typically act on integral membrane receptors, which translate the signal of the extracellular messenger into an intracellular signal.

  Receptor types

Intracellular receptors

• Definition

  receptors that are located inside the cell

• Examples

  • IP3-receptor
  • Nuclear receptors

Cell surface receptors

• what is it?

  Hydrophilic hormones transmit signals by binding to receptors present in the cell membrane (= cell surface receptors).

• G protein-coupled receptors

  G protein-coupled receptors (GPCRs) are the largest family of membrane receptors. The action of GPCRs depends on three elements: the receptor, the G protein, and the effector molecule

  • Examples of ligands
  • Receptor structure
  • G protein
  • Effector molecules

  Gs proteins activate adenylyl cyclase, whereas Gi proteins inhibit adenylyl cyclase!

  

• Enzyme-linked receptors

  • Receptor tyrosine kinases (RTKs)
  • Non-receptor tyrosine kinases

• Ligand-gated ion channels

  Since most ligands of ligand-gated ion channels are neurotransmitters, only a short overview is provided here.

  • Examples of ligands
  • Receptor structure:
  • Activation principle (example)

Second messengers

• what is it?

  Second messengers are small molecules that mediate the intracellular response to an extracellular stimulus.

• types

  • cAMP (cyclic adenosine monophosphate) and protein kinase A
  • cGMP (cyclic guanosine monophosphate)
  • Nitric oxide
  • IP3 and DAG
  • Ca2+

Regulator

protein scaffold adalah regulator penting dari banyak jalur pensinyalan kunci.

cari SH3 domain, SH2, protein rich, PH , zinc finger

Muscle fusion[edit]

Primary muscle fibers originate from primary myoblasts and tend to develop into slow muscle fibers.[4] Secondary muscle fibers then form around the primary fibers near the time of innervation. These muscle fibers form from secondary myoblasts and usually develop as fast muscle fibers. Finally, the muscle fibers that form later arise from satellite cells.[4]

Two genes significant in muscle fusion are Mef2 and the twist transcription factor. Studies have shown knockouts for Mef2C in mice lead to muscle defects in cardiac and smooth muscle development, particularly in fusion.[12] The twist gene plays a role in muscle differentiation.

The SIX1 gene plays a critical role in hypaxial muscle differentiation in myogenesis. In mice lacking this gene, severe muscle hypoplasia affected most of the body muscles, specifically hypaxial muscles.[13]