Protein kinase C

Definition

Protein kinase C (PKC) is a family of serine/threonine kinases that play critical roles in various cellular processes, including signal transduction, cell growth, differentiation, and apoptosis. PKC is activated by second messengers like diacylglycerol (DAG) and calcium ions, linking extracellular signals to intracellular responses and amplifying the effects of these signals.

5 Must Know Facts For Your Next Test

1. PKC exists in multiple isoforms, each with specific functions and tissue distributions, allowing for diverse cellular responses to different signals.
2. Activation of PKC often leads to changes in gene expression, influencing processes like inflammation and cancer development.
3. PKC can modulate the activity of other proteins by phosphorylating them, which can either activate or inhibit their functions depending on the target.
4. There are two main classes of PKC: conventional (cPKC) which requires calcium and DAG for activation, and novel (nPKC) which only requires DAG.
5. Dysregulation of PKC has been implicated in various diseases, including cancer, diabetes, and cardiovascular diseases.

Review Questions

• How does protein kinase C contribute to signal amplification in cellular signaling pathways?
  • Protein kinase C contributes to signal amplification by being activated by second messengers like diacylglycerol (DAG) and calcium ions. Once activated, PKC phosphorylates target proteins, leading to a cascade of downstream signaling events that amplify the original signal. This means a single extracellular signal can result in significant changes within the cell due to the multi-step activation process facilitated by PKC.
• Discuss the role of different isoforms of protein kinase C and how they impact cellular functions.
  • Different isoforms of protein kinase C (PKC) are distributed throughout various tissues and have distinct roles in regulating cellular functions. For example, cPKC isoforms are traditionally involved in calcium-dependent pathways, while nPKC isoforms respond to DAG independently of calcium. This diversity allows cells to fine-tune their responses to specific stimuli based on which PKC isoforms are activated, affecting processes such as growth, differentiation, and survival.
• Evaluate the implications of dysregulation of protein kinase C in disease pathology.
  • Dysregulation of protein kinase C can have significant implications for disease pathology. For instance, overactive PKC signaling has been linked to cancer progression through enhanced cell proliferation and survival. Conversely, insufficient PKC activity may contribute to diseases such as diabetes and cardiovascular issues by impairing normal signaling pathways that regulate metabolism and vascular function. Understanding these relationships highlights the potential for targeting PKC pathways in therapeutic strategies for various diseases.

Related terms

Diacylglycerol (DAG): A second messenger produced by the hydrolysis of phospholipids in the cell membrane, which activates protein kinase C.

Calcium Ions (Ca²+): Essential signaling molecules that, when elevated in the cytoplasm, contribute to the activation of protein kinase C and other signaling pathways.

Phosphorylation:

The process of adding a phosphate group to a protein, which can alter its function and activity, often mediated by kinases like PKC.