Making neural connections 3

Question 1

Location of semaphorins?

Answer 1

Majority of Semaphorins are membrane bound
Some Semaphorins are secreted and associate with cells or the ECM.

Question 2

Action of semaphorins?

Answer 2

Semaphorins act primarily as repellents but can be attractant in some cases.

Question 3

Semaphorin receptors?

Answer 3

Multiple transmembrane receptors–> must signal to the cytoskeleton
Limited number of types

Question 4

How is the reaction to the same signal from the same receptor chagned?

Answer 4

Alterations to other aspects of the cells biology in diff neurons

Question 5

What is a semaphorin characterised by?

Answer 5

Sema domain - highly conserved – 500 amino acids in size.

Question 6

Name of the transmembrane receptors for semaphorins?

Answer 6

Plexins

Question 7

How do the transmembrane semaphorin bind to plexins?

Answer 7

Directly

Question 8

How do the secreted semaphorin bind to plexins?

Answer 8

Require an additional protein (Neuropilin) to bind to the Plexin

Question 9

Effect of most semaphorins on the growth cone?

Answer 9

Repellant

Question 10

Different effects of SemaIII on neurite growth depending on what is rpesent?

Answer 10

NGF present–> SemaIII has a repellent effect
NT3 present–> SemaIII elicits outgrowth

Question 11

How can the same signal and same receptor give different outcomes?

Answer 11

The environment they are present in can change how the signals are interpreted