Week 3- Cell Signalling Flashcards
Why do cells communicate?
Haemostasis, voluntary movement, to process information, self preservation
What is the response to hypoglycaemia? What type of response is this?
Glucagon released from alpha cells in islets of langerhans in the pancreas. Causes glycogenlysis, gluconeogenesis in liver. It is endocrine communication
What targets does insulin work on?
Liver, muscle cells, adipose tissue
What targets does adrenaline work on?
Trachea
Where is adrenaline produced?
Adrenal gland
What is the response to hyperglycaemia? What type of response is this
Insulin is released from beta cells in islets of langerhand in pancreas, it inhibits glucagon secretion, reduces gluconeogenesis, glycogenolysis etc. It is a paracrine response
Describe the signaling pathway between membrane attached proteins when a foreign antigen is encountered
The pathogen containing the foreign antigen is phagocytosed and its antigen is displayed on the surface of the phagocyte via the major histocompatibility complex (class II molecules). This MHC then interacts with T cell receptors
Describe the pathway of events in T cells after T cell receptors interact with a MHC
A signaling cascade is activated in the T cell wherein interleukin 2 receptors are displayed on the cell surface. Il2 itself is also synthesized and secreted, it binds to receptors in the same cell and adjacent cells thereby activating lots of T cells
What are the 4 different types of receptors?
Ionotropic, G protein coupled, enzyme linked and intracellular
Describe how ionotropic receptors work
Binding of ligand causes a conformational change that opens a pore. This pore allows ions to travel through depending on concentration gradient
Describe how G protein coupled receptors work
Both receptor and heterotrimer G protein are inactive
Binding of ligand causes a conformational change in receptor shape
G protein binds to receptor and bound GDP is phosphorylated to GTP
G protein dissociates into alpha and beta/gamma subunit
Alpha subunit with bound GTP binds to target molecule
Intracellular signaling cascade is triggered
GTPase on alpha subunit converts GTP back to GDP
Alpha subunit dissociates from target molecule and inactivates the signaling cascade so it isn’t continuous
Describe how enzyme linked receptors work
Binding of ligand causes a conformational change
This change causes receptors to cluster
Receptor clustering activates an enzyme
The enzyme phosphorylates receptors causing binding of signaling proteins to the cytoplasmic domain
Signaling proteins recruit other signaling molecules until a signal is generated
Signal is terminated when phosphotase enzyme dephosphorylates the receptors
What are the 2 types of intracellular receptors?
Cytoplasmic and nuclear
Describe how cytoplasmic intracellular receptors work
Receptors are in the cytosol and are associated with a chaperone molecule eg heat shock protein (hsp). Ligand binding causes hsp to dissociate and 2 hormone bound receptors form a homodimer. This can enter the nucleus and bind to DNA, altering transcription
Describe how nuclear intracellular receptors work?
Located in the nucleus, ligand binding changes transcription
