Cell Signaling

________ is the conversion between signaling molecules

Signal transduction

_________ signaling is long range, systemic, and involves hormones

Endocrine

_______ is a hormone made in the pancreas, secreted into the _________, and regulates glucose uptake throughout the body

Insulin, bloodstream

Adrenalin, melatonin, estrogen, and testosterone are examples of _________

Hormones

________ signaling goes from cell to cell by proteins secreted into extracellular space

Paracrine

Paracrine signaling can be short or longer range, and is moved between cells and tissues by ________.

Diffusion

_______ signaling is important for patterning the developing embryo, in wound healing, and in cancer

Paracrine

__________ signaling is a type of paracrine signaling in which a cell receives the signal it makes.

Autocrine

When cancer cells promote their own uncontrolled growth via self-signaling, this is known as _______ signaling.

Autocrine

_________ signaling is signaling from neurons to other cells.

Synaptic

In synaptic signals, ________ like dopamine, glutamate, and gabapentin are released as a local signal in the synapses of 2 cells. This process is extremely fast (~100 m/s)

Neurotransmitters

_________ signaling is direct, physical contact between cells. The signal never leaves the signaling

Contact-dependent

_________ signaling is very common in the immune system, and is also essential for embryo development.

Contact-dependent

A type of contact dependent signaling is known as _____/_____ signaling. The signal on one cell binds to the receptor on another. The ______ cleaves into 2 proteins, which travels to the nuclear and a functions as a ___________

Delta/notch, notch, transcription factor

__________ receptors are for signals too big/hydrophilic to cross the membrane, and need receptors to transfer the signal

Cell-surface

__________ receptors are very small or hydrophobic and can cross the membrane, allowing them to bind receptors/enzymes directly

Intracellular

What is the difference between intracellular receptors and extracellular receptors/signals?

Extracellular signals require a cell-surface receptor to translate the signal into a cell due to size/polarity of signal being unable to cross the membrane

Intracellular signals are small, and so they can pass through the membrane directly

How do cells know which signals to respond to?

1. Different cells can express different receptors

2. Within a cell, signal transduction can be different

Provide an example of how a signal can be interpreted differently by different cells.

Acetylcholine bound to heart pacemaker cells decreased heart rate.

When binding to salivary gland cells it causes vesicles to fuse, releasing saliva.

When it binds to skeletal muscle cells, it leads to contraction.

What happens to cells in the absence of signals?

Death via apoptosis

True or false: different combinations of signals will cause cells to act differently than they would with each signal in isolation.

True

What is the key difference between fast and slow responses to signaling?

Whether or not transcription/translation are needed for the response to signaling

True or false: steroids do not cross membranes due to their size and polarity

False

__________ hormones like cortisol can cross the plasma membrane and bind directly to receptors in the cytoplasm. These receptors relocate to the nucleus and act as ________ _______

Steroid, transcription regulators

What are the 5 general processes for extracellular receptor transduction?

1. Relays

2. Amplifiers

3. Integrators

4. Distributors

5. Feedback

What do relay receptors do?

Convert signal from one site to another

What do amplifier receptors do?

Receive a signal and transmit many more signals

What do feedback receptors do?

They feed back into earlier steps in the cascade, either dampening it (negative feedback) or encouraging it (positive feedback)

What do distributor receptors do?

Assist the signal in reaching its final result

What do protein phosphorylation and GTP-binding proteins signals have in common?

They are typically activated by the addition of a phosphate group

What are the 3 Types of extracellular receptors?

1. Ion channels coupled receptors

2. G-protein'-coupled receptors (GPCRs)

3. Enzyme-coupped receptors

How do ion channels coupled receptors work?

A chemical signal causes a channel to open, allowing ions to flow. This converts chemical signals to electrical signals

What is an example of an ion channels coupled receptor signal?

Glutamate. It binds to an ion channels coupled receptor, allowing Na+ to flow into the cell

These are the target of money recreational drugs and common medications

Too much glutamate can be toxic and is link to amyotrophic lateral sclerosis (ALS), and schizophrenia

How many transmembrane domains do g-protein-coupled receptors have?

7

What do alpha subunits do in GPCRs?

The binding of the receptor changes the confirmation of the receptor, allowing it to bind to the alpha subunits. The alpha subunits releases its GDP, and then picks up GTP, becoming activated. When it picks up GTP, the beta and gamma can fall off

The alpha is deactivated by hydrolysis of GTP (gap protein)

GPCRs usually are which type of receptors due to their second messenger molecules?

Amplification receptors

What is an example of a GPCR and how does it work?

Cyclic AMP (cAMP)

cAMP is a derivative of ATP. It forms a phosphate ring when exposed to adenylyl cyclase (activates by the GTP-bound alpha subunit). Cyclic AMP phosphodiesterase breaks this ring, converting it to AMP

cAMP can bind to and activate enzymes like Protein Kinase A, which can phosphorylated other proteins. For example this is how adrenaline causes breakdown of glycogen in muscles cells

What does adenylyl cyclase do?

Converts ATP to cAMP

What is the relationship between opioids and GPCRs?

Opioids bind to GPCR receptors in the brain