Lecture 23 - Cell Communication

What are the three stages of cell signaling?

1. Reception, 2. Transduction, 3. Response[cite: 2]

What is a cellular response?

A change in a cell's behavior, activity, or state (can be temporary or permanent) after signal detection[cite: 4]

What are some possible outcomes of a cellular response?

Altering gene expression, activating/inhibiting enzymes, changing metabolism, secreting molecules, moving/changing shape, and initiating cell division or apoptosis[cite: 4]

What are the characteristics of a cytoplasmic response?

Fast response (seconds to minutes), short-lived/temporary, acts on pre-existing proteins via modifications like phosphorylation[cite: 5]

What is an example of a metabolic/cytoplasmic response to epinephrine?

Glycogen breakdown (glycogenolysis) into glucose to provide immediate energy production[cite: 5, 12]

What enzyme is activated by cAMP during the epinephrine metabolic pathway?

Protein kinase A (PKA)[cite: 6]

What are the characteristics of a nuclear response?

changes gene expression, slow response (minutes to hours), long-term (can be permanent), completely modifies how a cell looks and responds, and requires transcription and translation[cite: 7]

What are the outcomes of a nuclear response?

Cell proliferation, cell differentiation, production of new enzymes, and production of new receptors[cite: 7]

In the Ras/MapK pathway, what active protein crosses the nuclear membrane to activate cell division?

ERK (via phosphorylation)[cite: 8]

What does the transcription factor c-Myc promote when active?

The transcription of genes involved in cell division (cell proliferation)[cite: 8]

What does MNK1 promote when active?

Increased translation of certain mRNAs involved in cell division[cite: 8]

Does the signaling molecule/signal alone determine the cellular response?

No, the cellular response is determined by the receptor and downstream proteins, not by the signal itself[cite: 9, 12]

Why do different cells have different responses to the same signal (Specificity)?

Different kinds of cells have different collections of proteins and receptors[cite: 10, 11]

What happens in Cell A during signaling specificity?

The pathway leads to a single response[cite: 10, 11]

What happens in Cell B during signaling specificity?

The pathway branches, leading to two responses[cite: 10, 11]

What happens in Cell C during signaling specificity?

Cross-talk occurs between two pathways (activation or inhibition)[cite: 10, 11]

What happens in Cell D during signaling specificity?

A different receptor leads to a completely different response[cite: 10, 11]

What is signal branching?

When a single signaling pathway/receptor leads to the regulation of multiple cellular activities or outcomes[cite: 13]

What is cellular crosstalk?

Interactions between different signaling pathways that allow cells to integrate multiple signals and fine-tune precise, coordinated responses[cite: 15]

What role does p38 play in crosstalk?

It participates in insulin signaling by integrating stress-related signals with the PI3K-Akt and Ras-MAPK pathways[cite: 15]

What does a Standard Arrow (→) represent in signaling pathways?

Activation, stimulation, or positive regulation[cite: 17]

What does a T-Bar Arrow (⊣) represent in signaling pathways?

Inhibition or blocking of protein activity[cite: 17]

What does a Dashed Arrow (⇢) represent in signaling pathways?

An indirect effect, a multi-step process, or a predicted interaction with unshown intermediate steps[cite: 17]

What does a Line / Simple Connector represent in signaling pathways?

A binding or physical interaction without specifying direct activation or inhibition[cite: 17]

What does a Loop / Curved Arrow represent in signaling pathways?

Translocation (a protein moving from the cytosol to the nucleus or another cellular compartment)[cite: 17]

What are the major mechanisms used for signal termination?

Removal of the signal (ligand), receptor inactivation or downregulation, inactivation of transducers, removal of second messengers, and protein degradation[cite: 18]

What are outcomes of cytoplasmic responses

cytoskeletal remodeling, alteration of cellular transport, alternation of enzyme activity, disruption of membrane potential, alteration of metabolism