Protein Kinase A

Definition

Protein Kinase A (PKA) is an enzyme that plays a crucial role in cellular signaling by phosphorylating specific serine and threonine residues on target proteins, thereby altering their activity. PKA is activated by cyclic AMP (cAMP), a second messenger involved in various signal transduction pathways, allowing it to influence numerous physiological processes such as metabolism, gene expression, and cell growth.

5 Must Know Facts For Your Next Test

1. PKA is composed of two regulatory subunits and two catalytic subunits; the binding of cAMP to the regulatory subunits causes a conformational change that releases the catalytic subunits for activation.
2. PKA is involved in the regulation of glycogen metabolism, influencing glycogen breakdown and synthesis depending on hormonal signals such as adrenaline.
3. The action of PKA can lead to changes in gene expression by phosphorylating transcription factors, impacting cellular functions over longer time frames.
4. In addition to metabolism and gene expression, PKA also plays roles in cell division, muscle contraction, and the modulation of ion channels.
5. Dysregulation of PKA activity has been linked to various diseases, including cancer, diabetes, and heart disease, highlighting its importance in maintaining cellular homeostasis.

Review Questions

• How does Protein Kinase A get activated and what are its main functions in cellular signaling?
  • Protein Kinase A (PKA) is activated when cyclic AMP (cAMP) binds to its regulatory subunits, causing a change that releases the catalytic subunits. Once activated, PKA phosphorylates target proteins on serine and threonine residues, which can alter their function. This phosphorylation impacts several cellular processes such as metabolism regulation, gene expression, and muscle contraction, illustrating its vital role in cellular signaling pathways.
• Discuss the relationship between cyclic AMP and Protein Kinase A in the context of signal transduction.
  • Cyclic AMP acts as a crucial second messenger in signal transduction pathways by activating Protein Kinase A (PKA). When hormones or neurotransmitters bind to their receptors on the cell surface, they trigger an increase in cAMP levels within the cell. This elevated cAMP then binds to the regulatory subunits of PKA, leading to its activation. The activated PKA can then phosphorylate various target proteins, translating the extracellular signal into a specific intracellular response.
• Evaluate the implications of Protein Kinase A dysregulation in disease states and potential therapeutic targets.
  • Dysregulation of Protein Kinase A (PKA) has significant implications in various disease states such as cancer, diabetes, and cardiovascular diseases. Abnormal PKA activity can disrupt normal cellular processes like metabolism and cell growth, contributing to disease progression. As such, targeting PKA or its signaling pathways represents a promising area for therapeutic interventions. By restoring proper PKA function or inhibiting its aberrant activity, it may be possible to improve treatment outcomes for patients suffering from these conditions.

Related terms

Cyclic AMP: Cyclic AMP (cAMP) is a second messenger molecule that transmits signals from hormones and neurotransmitters to the inside of cells, activating various signaling pathways.

Phosphorylation: Phosphorylation is the process of adding a phosphate group to a protein or other organic molecule, which often alters the function and activity of the target molecule.

Signal Transduction: Signal transduction refers to the process by which cells respond to external signals, involving a series of molecular events that lead to a cellular response.