Cell Signaling Basics (Receptors, Second Messengers) - Anatomy and Physiology
- What type of signaling occurs when a cell responds to a chemical it secreted itself?
- Autocrine signaling. Paracrine signals act on nearby cells instead.
- Which kinase does diacylglycerol (DAG) activate, together with Ca2+?
- Protein kinase C (PKC).
- How is a G protein switched on and off?
- It is active when its alpha subunit binds GTP, and turns off when it hydrolyzes GTP to GDP.
- Which protein kinase does cAMP activate?
- Protein kinase A (PKA), which phosphorylates target proteins.
- Which enzyme does a Gs protein activate, and which second messenger results?
- Adenylyl cyclase, which converts ATP to cyclic AMP (cAMP).
- Where are the receptors for steroid hormones located, and how do they act?
- Inside the cell (cytoplasm or nucleus). The hormone-receptor complex acts as a transcription factor that changes gene expression.
- What are the three main classes of cell-surface receptors?
- G protein-coupled receptors, enzyme-linked receptors (such as receptor tyrosine kinases), and ligand-gated ion channels.
- Which enzyme breaks down cAMP to end the signal?
- Phosphodiesterase, which converts cAMP to inactive AMP.
- What effect does an activated Gi protein have on adenylyl cyclase?
- It inhibits adenylyl cyclase, lowering cAMP levels.
- A drug inhibits phosphodiesterase. How does this change the response to a hormone that raises cAMP?
- The response is larger and longer, because cAMP is broken down more slowly.
- Which enzyme does a Gq protein activate, and what does it produce?
- Phospholipase C, which cleaves PIP2 into IP3 and diacylglycerol (DAG).
- What does IP3 do inside the cell?
- It binds receptors on the endoplasmic reticulum and releases stored Ca2+ into the cytoplasm.