6- signalling Flashcards
What is the role of PI3K in cell signaling, and how is it activated?
PI3K (Phosphoinositide 3-kinase) attaches to activated receptors via its SH2 group and is activated by RAS-GTP. It phosphorylates inositol-containing phospholipids in the plasma membrane, producing PIP2 or PIP3, which can activate downstream signaling pathways.
How does the PI3K pathway contribute to cancer, and what mutations are observed in cancer patients?
Mutations in PTEN or PI3K have been observed in cancer patients. The PI3K pathway is involved in cell proliferation and survival, and dysregulation of this pathway can contribute to cancer development.
Describe the MAPK pathway and its components.
The MAPK (Mitogen-Activated Protein Kinase) pathway involves Ras, Raf, MEK, and ERK. Ras activates Raf, which phosphorylates MEK, and MEK activates ERK. ERK acts as a transcription factor, turning on genes involved in cell proliferation.
What is paracrine signaling, and how does it relate to cancer?
Paracrine signaling involves secreted signal molecules acting locally on neighboring cells. In cancer, fibroblasts in the stroma release growth factors that act on nearby cancer cells, contributing to tumor growth.
Define growth factors and growth factor receptors.
Growth factors are extracellular proteins that promote cell growth, proliferation, differentiation, or survival. Growth factor receptors, like receptor tyrosine kinases (RTKs), are activated by ligands, leading to signaling cascades within cells.
Explain the activation of RTKs and their role in signaling.
How do the Ras-ERK and PI3K-AKT pathways stimulate cell metabolism?
Ras-ERK and PI3K-AKT pathways influence metabolism via Myc and Akt, respectively. They regulate processes such as glucose uptake, glycolysis, nucleotide, and amino acid synthesis, affecting cell growth.
What are oncogenes and tumor suppressor genes, and how do they contribute to cancer?
Oncogenes have the potential to cause cancer, while tumor suppressor genes protect cells from progressing toward cancer. Mutations in oncogenes (e.g., RTKs) can lead to uncontrolled signaling, and mutations in tumor suppressor genes (e.g., PTEN) can allow cancer development.
Card 9:
How do the Ras-ERK and PI3K-AKT pathways regulate migration and invasion?
These pathways regulate migration and invasion through downstream effectors, including Rho-family GTPases, integrins, extracellular proteases, cell-cell adhesion complexes, and transcription factors. Dysregulation contributes to metastasis
What is Epithelial-Mesenchymal Transition (EMT), and how does it relate to cancer?
EMT is a process where normal epithelial cells change shape and acquire mesenchymal characteristics, facilitating metastasis. Ras-ERK and PI3K-AKT pathways play roles in regulating EMT.
What role does the tumor microenvironment play in tumorigenesis and cancer therapy?
The tumor microenvironment influences tumorigenesis and can alter the response of cancer cells to therapy, including inhibitors targeting Ras-ERK and PI3K-AKT pathways.
