Lecture notes
Thyroid hormone signalling
- Institution
- Aston University, Birmingham (Aston)
In depth cell signalling and physiology notes, created using synchronous and asynchronous material.
[Show more]
Seller
Follow
Content preview
Thyroid hormone signalling.How are thyroid hormones made?
Thyroid hormones are made from the amino acid tyrosine.
Tyrosine is modified by the addition of the iodine groups. (Tyrosine is iodinated).
This forms two different forms of the thyroid hormone: thyroxine (T4) or
triiodothyronine (T3).
Thyroid hormone is not a peptide hormone or a signalling hormone it is an amino
acid hormone.
Thyroid hormone signalling pathway.
Thyroid hormone needs to cross the hydrophobic cell membrane to cross the cell.
Thyroid hormones are hydrophobic so they can readily cross the cell membrane.
Thyroid hormones can also be transported via specialist membrane transporters.
The presence of the transporters gives us a way of regulating thyroid hormone
signalling.
This is because the expression of the membrane transporters, is regulated both in
space, so they are expressed in high levels ion certain tissues, we can also regulate
their expression over time, for example, especially during foetal development, we
can see high levels of these transporters are in expressed in certain tissues at certain
points.
This means that we can control thyroid hormone signalling at the level at which the
thyroid hormone can enter the cell by changing where and when these membrane
transporters for the thyroid hormone are expressed.
Once the thyroid hormone has entered the cell, we see local activation.
The T4 form of thyroid hormone is less active than the T3 form.
So once T4 enters the target cell it can be converted to T3 through the activity of the
deiodinases enzymes (D1/D2).
T4 is converted to T3 through the activity of D1/D2 deiodinases but it can also be
converted into an inactive form of T3 called reverse T3 (rT3), by the type 3 5-
deiodinase (D3) enzyme.
The activity of the deiodinase enzymes is highly regulated, they can be ubiquinated
on certain lysine residues and the ubiqitation targets them for degradation via the
proteosome.
Thyroid hormone needs a receptor to function, the receptor for thyroid hormone is
the thyroid hormone receptor (THR).
There are multiple isoforms for this receptor, but they are all expressed from a single
thyroid hormone receptor gene.
All the isoforms are members of a superfamily of receptors called the nuclear
hormone receptors.
Although there are multiple isoforms, they do share some common sequences, or
functional domains.
They all contain a region that allows them to bind directly to the DNA and they all
contain a region that allows them to bind to T3.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller sarah21jan. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £6.46. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
84866 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now