Cell Signaling Mechanisms Quiz

Cell Signaling (Continued)

• Cyclic AMP (cAMP) activation through GPCRs involves a cascade: A signal molecule activates a G protein-coupled receptor (GPCR), which activates adenylyl cyclase. Adenylyl cyclase converts ATP to cAMP. cAMP activates protein kinase A (PKA). PKA then phosphorylates CREB, which binds to the cyclic AMP response element (CRE) on DNA, initiating gene transcription.

• PLC/PKC signaling: A signal activates phospholipase C, which cleaves a membrane phospholipid (PI(4,5)P2) into diacylglycerol (DAG) and inositol 1,4,5-trisphosphate (IP3). DAG activates protein kinase C (PKC). IP3 releases calcium ions from the endoplasmic reticulum. Calcium and calmodulin regulate downstream kinase activity.

• Calcium/Calmodulin controls downstream kinase activity: Calcium ions bind to calmodulin, causing a conformational change in calmodulin. This activated calmodulin complex then interacts with and regulates target proteins, including kinases, affecting cellular processes.

• Calcium transients trigger many cellular processes: Calcium release is triggered by various signals, not just GPCRs. These calcium signals regulate diverse processes including skeletal muscle contraction, neurotransmitter release, fertilization, and more.

• PLC initiates calcium waves in egg activation: Phospholipase C (PLC) triggers calcium waves in egg activation, playing a crucial role in the process.

• Calcium waves propagate through feedback: IP3 receptors require both IP3 and calcium to function efficiently, leading to a cascade of calcium release and propagation throughout the cell and potentially between cells.

• How do signaling waves propagate across many cells?: There are examples of wound repair and cellular processes where signaling waves travel across multiple cells.

• Smell and Vision Depend on GPCRs That Regulate Ion Channels: Olfactory neurons and photoreceptors rely on GPCRs to regulate ion channels, enabling sensory perception.

• Signals are amplified by cascades: Photoreceptor signaling amplifies light signals by activating multiple proteins in a cascade. A single photon of light can trigger a large change in the membrane potential of the cell, transmitting a signal to the brain.

• There is cross-talk between many signaling pathways and types of receptors: Different signaling pathways intersect and influence each other.

• JAK-STAT signaling: Cytokine binding activates JAKs, which phosphorylate STAT proteins. These phosphorylated STATs then dimerize, translocate to the nucleus, and regulate gene transcription.

• Lab and closing remarks: The next section will cover plant cell culture, and the final exam will include the material from this section along with previous sections.

Test your knowledge on key cell signaling pathways such as cyclic AMP (cAMP) activation and phospholipase C (PLC)/protein kinase C (PKC) signaling. This quiz covers the details of how signaling molecules activate receptors and the subsequent cellular responses. Ideal for students studying cell biology or biochemistry.