Lecture 9: Cell Signaling Pt.1

Signal Transduction

when a signal interacts with a recprotr causing changes inside the cell

Types of cellular signaling

1. Endocrine (long distance and public)

2. Paracrine (Local and short)

3. Neuronal (long distance and discrete)

4. Contact Dependent (short& specified)

Endocrine Signalling (SHOUTING)

• hormones are secreted and pushed widely throughout the entire body, looking for it’s target 

• wide broadcast SHOUTING

Hormones

an extracellular signal secreted & transported via the bloodstream to target cells and have an effect!! 

Paracrine Signaling (LOCAL signaling) 

• same idea as endocrine but it much more local

• a local mediator diffuses and signals to NEARBY cells

• if a cell produces a signal and responses to it itself, AUTOCRINE signaling  

Neuronal Signaling (long but discrete)

• electrical signals are sent though & broadcast very specifically over a long distance 

Contact Dependent Signaling (KISSING) 

• one cell pushes out a signal but doesn't let it go and another cell has a receipt for it 

• Requires the cells to touch and hold one another 

Receptors

• something in the plasma membrane that recognizes & receives signals

• sometimes a receptor can be in the cytosol meaning that the signal can diffuse through if small enough

True or false:the same signal can have a different effect on different things

• True 

Signals can effect… list them 

• cell shape 

• movement 

• metabolism 

• gene expression 

• proliferation 

• survival 

• differentiation

What does the response time of a signal depends on

the effect the signal has

• if it is altering a protein it is fast

• if it altering protein synthesis (transcription & translation) it is very slow

Scaffolds

• proteins that hold certain proteins close so that they can participate in cell signaling pathways more efficiently 

Amplifiers 

• some proteins react to signals by pushing out more signals, to amplify 

True or false: some receptors need multiple signals to continue the pathway

TRUE

Positive Feedback

when a component downstream acts on a component upstream to ENHANCE response 

Negative Feedback 

a component that leis downstream acts on a component upstream to INHIBIT response

True or false: Proeins can act as a molecular switches, being turned on or off using phospoliraltion or GTP

TRUE 

Signaling By Phosphorylation

• when a kinase adds a phosphate group or when a phosphatase removes a phosphate group

• can turn a protein on OR off

Signallign by GTP-Bindign

• when GTP is bound the protein is “on” but when GDP is bound the protein is “off”

Autocrine signaling

• a subset of paracrine signaling where a cell reacts to the signal it itself produces