Unit 7 Flashcards
Signal transduction is the process of converting an extracellular (_______ A) into an intracellular signal (______ B) in a _______.
Signaling molecule A,
Signaling molecule B,
Target cell
Cells communicate by means of:
extracellular signaling molecules
Intracellular signal can initiate series of intracellular rxn’s that regulate: (6 examples)
Transcription,
Survival,
Protein synthesis,
Movement,
Cell death,
Metabolic changes
Six steps in signaling
- Signaling molecule synthesis by signaling cell
- Signaling molecule released by signaling cell
- Signaling molecule transport to target cell
- Signal detection by specific receptor protein
- Change in cellular metabolism, function, or development triggered by the receptor-signaling molecule complex
- Removal of signaling molecule; Terminating cellular response
Signaling can be classified into 4 types that act over short or long distances:
- Autocrine signaling
- Paracrine signaling
- Endocrine signaling
- Contact-dependent signaling
Autocrine signaling definition
Cells respond to SM’s that they release themselves.
Autocrine signaling is common in:
cancer cells, which overproduce and release growth factors that stimulate inappropriate, unregulated growth and division of themselves, leading to cancer development
Paracrine signaling definition
SM’s released by signaling cell into the extracellular medium act locally to affect target cells in close proximity to the signaling cell
Endocrine signaling definition
SM’s (hormones), act on target cells distant from their site of synthesis by endocrine cells.
Hormones made in endocrine cells secreted into blood stream & can be distributed widely throughout body.
Contact-dependent signaling definition
A membrane-anchored signal in plasma membrane of the signaling cell binds to a receptor molecule embedded in the plasma membrane of the target cell.
What does contact-dependent signaling require?
Requires cells to be in direct membrane-to-membrane contact with each other and does not require the release of a signaling molecule.
Which of the four signaling mechanisms can be glycosylated?
Contact-dependent signaling
The extracellular signaling molecule alone is not the signal. The signal depends on:
How the target cell interprets the signaling molecule, which is dictated by intracellular signaling pathways.
Signaling pathways consist of a series of:
Proteins (&/or) 2nd messengers
Each protein in a pathway alters the ____ or ______ of the next protein. In some cases, the intracellular signaling molecule can be a small molecule (e.g. cAMP, Ca2+). These are referred to as ______.
Conformation,
Activity,
2nd Messengers
Protein conformation in intracellular signaling is usually altered by _______.
Phosphorylation: If something (generally) gets phosphorylated in a protein activation pathway, that protein becomes active
____ add phosphate groups, while ______ remove them. Very often signaling proteins rely on _______.
Kinases,
Phosphorylases,
Protein kinases
When signaling is mediated by proteins, upon activation of the signaling cascade there are four types of molecular switches: (To turn on/off signaling pathway)
- Phosphorylation / dephosphorylation
- GTP-binding
- Assembly-Disassembly of protein complexes
- Proteolysis
Which is the only irreversible of the four molecular switches during cellular signaling mediation:
Proteolysis
Four ways protein phosphorylation can change protein behaviour:
- Activate/inactivate an enzyme.
- Promote/interfere with protein-protein interactions.
- Change the subcellular location of the protein.
- Trigger protein degradation.
Kinase _____’s a signal, and phosphatase _____’s a signal
Activate,
Inactivate
GTP binding as a molecular switch example
GPCR
In the absence of a signal, the GTP-binding protein is bound to ___. Signals activate the release of it and the subsequent binding to ___.
GDP,
GTP
A GTP-binding protein is ___ when bound to GTP and _____ when bound to GDP.
Active,
Inactive
Difference between the Rab vs. GTP binding proteins
Rab family are single polypeptides
GTP-binding proteins are heterotrimeric
in GTP binding, the ____ activity of these intracellular signaling proteins hydrolyses the bound ____ to GDP and Pi, thus converting the _____ form back to the _____ form.
GTPase,
GTP,
Active,
Inactive
Many signal-transduction cascades contain multiprotein signaling complexes that _____ and ______ protein complexes
Assemble,
Dissassemble
