Cell signalling by cytokine receptors Flashcards
what are cytokines?
a broad range of signalling molecules
what are some examples of cytokines?
proteins, peptides, and glycoproteins
includes interferons and interleukins plus additional factors
what are cytokines involved in?
Autocrine, paracrine and endocrine signalling
what produces interleukins?
cells that have suffered damage
how do cytokines act on cells?
cytokines act via cell surface cytokine receptors
what is growth hormone?
peptide hormone (also called somatotropin) produced by somatotrophic cells in the anterior pituitary
what signal increases the release of growth hormone?
GH-releasing hormone released from the hypothalamus
Ghrelin for the stomach
what signal inhibits the release of growth hormone?
GH-inhibiting hormone (SS) also released from the hupothalamus
where is growth hormone produced?
by the somatotrophic cells in the anterior pituitary
what are the effects of growth hormone on the body?
Growth hormone has anabolic effects including muscle and bone growth
many Growth hormone actions are secondary to its ability to stimulate insulin-like growth factor 1 (IGF-1) release from the liver
what is the process of growth hormone receptor signaling?
-Growth hormone binds to the growth hormone receptor on the surface of target cells, including the liver hepatocytes
- this causes two growth hormone receptors to come together and dimerize
- this dimerized receptor complex becomes active because the associated JAK2 proteins come into contact with each other
-JAK2 is a protein tyrosine kinase and when activated adds phosphates to intracellular signaling molecules including STAT5 and ERK1/2
-Phosphorylated STAT5 and ERK1/2 enter the nucleus and act as transcription factors turning on (or off) specific genes
when does growth hormone receptor become active?
when growth hormone binds and the receptors dimerize
-the dimerized receptor becomes active because the associated JAK2 proteins come into contact with each other
what is JAK2?
JAK2 is a protein tyrosine kinase
what is the function of JAK2 once activated?
When activated JAK2 adds phosphates to intracellular signalling molecules including STAT5 and ERK1/2
what is the role of phosphorylated STAT5 and ERK1/2?
enter the nucleus and act as transcription factors turning on (or off) specific genes
what is the role of phosphorylated STAT5 and ERK1/2 in hepatocytes?
this would include increasing the production of IGF-1
what are STATs?
Signal Transducers and Activators of Transcription
what are the two forms of STAT5?
STAT5a and STAT5b which are very closely related
what pathway is STAT5 involved in?
part of the GH signalling pathway
what happens when STAT5 is phosphorylated?
When phosphorylated by JAK2 phospho-STAT5 (pSTAT5) may form homo or heterodimers
what happens to pSTAT5 dimers?
once in the nucleus, the pSTAT5 dimers interact with transcription factor (GR) which is activated by glucocorticoids to turn on specific genes
what happens when pSTAT5 enters the nucleus?
pSTAT5 dimers interact with a transcription factor which is activated by glucocorticoids to turn on specific genes
what activates transcription factor in the JAK/STAT pathway?
activated by glucocorticoids
what turns off the pSTAT5 response?
intracellular negative feedback pathways
how do STAT5 dimers enter the nucleus?
through the nuclear pore
