Hormone Action L-35

What are hormones?

Chemical messengers that regulate cell behavior.

Name the 3 hormone superfamilies.

1- Amino Acid Derivatives

2- Peptide hormones

3- Steroid hormones

What are the 2 major hormone receptor classes?

1- Cell surface receptors

2- Intracellular receptors

What happens when a ligand binds an intrinsic tyrosine kinase receptor (Intrinsic TK receptor)?

Dimerisation and autophosphorylation.

Name 2 intrinsic tyrosine kinase receptors.

1- Insulin receptor

2- EGF receptor

Describe the JAK-STAT signalling pathway.

1- Hormone binds receptor

2- Receptor dimerises

3- JAKs phosphorylate each other + receptor

4- STAT proteins dock + phosphorylate

5- STAT dimerises

6- Enter nucleus + regulate gene transcription

Describe the GPCR signalling pathway.

1- Hormone binds GPCR

2- GDP replaced by GTP on Ga

3- G-protein splits/dissociates

4- Effector enzyme activated

5- Second messengers (cAMP or IP3/DAG)

6- Protein kinase activated

7- Celular response

Name 4 second messengers.

1- cAMP

2- IP3

3- DAG

4- Ca2+

Describe steroid hormone signalling,

1- Hormone diffuse into cell

2- Binds to receptor

3- Complex enters nucleus

4- Binds to DNA

5- Alters transcription

Why is steroid hormone action slow but long-lasting?

It changes gene expression and protein synthesis.

What do nuclear receptors bind on DNA?

Hormone response elements (HREs) + regulate gene expression.

What is receptor desensitisation?

Reduced response after prolonged hormone exposure.

Why does insulin resistance occur?

Down-regulation or impaired signalling of insulin receptors.

Name 3 signalling pathways activated by EGFR.

1- Ras-Raf-MEK-ERK

2- PI3K

3- JAK-STAT

NAme the 3 structural parts of EGFR.

1- Extracellular ligand-binding domain

2- Single transmembrane helix

3- Cytoplasmic kinase domain

Where are intracellular receptors located?

Cytoplasm or nucleus.

What is the nuclear receptor superfamily?

A group of transcription factors activated by hormones.

Why can small amounts of hormones have large effects?

Signal amplification in intracellular cascades.

Why are peptide hormones fast-acting?

They use membrane receptors and signalling cascades.

What are the 3 major signalling mechanisms of hormone receptors?

1- Tyrosine kinase (TK) receptors

2- GPCRs

3- Intracellular (nuclear) receptors