B11 Week 10

• Gene therapies


  Use introduction/alteration of DNA sequences to create a therapeutic benefit

  
• Gene therapies are not new, but CRISPR/Cas9 is making this much easier and more precise, which is opening up new possibilities

  
• Gene therapies using viruses to introduce new DNA sequences to integrate randomly into the genome have been around for awhile and are still used routinely
• Regenerative medicine


  Seeks to restore tissue structure and function and provide options for what were previously untreatable injuries or diseases
• Regenerative medicine approaches can involve cell therapy, gene therapy, and/or tissue bioengineering
• Sickle cell disease


  An inherited blood disorder caused by a single nucleotide change that alters a single amino acid in the gene for β-globin, a subunit in hemoglobin, causing abnormal clumped protein fibers

  
• CRISPR gene therapy for sickle cell disease

  Patient's hematopoietic stem cells are isolated and edited to correct the single nucleotide change, then re-introduced to the patient after chemotherapy to remove existing unedited hematopoietic stem cells

  
• Induced pluripotent stem cells (iPSCs)

  Discovered in 2012, these are master regulators of pluripotency

  
• Cord blood is FDA approved as a source of hematopoietic stem cells to treat diseases of the blood/immune system (ex. leukemia and sickle cell anemia)

  
• The only stem cell products that are FDA-approved for use in the United States consist of blood-forming stem cells
• Autocrine, juxtracrine, and endocrine signaling pathways

  Types of cell-to-cell communication

  
• Cell surface vs nuclear receptors

  • Cell surface receptors mediate rapid signaling responses, nuclear receptors are transcription factors that regulate gene expression

  
• ECM and integrin signaling can influence cell function and cell survival
• Morphogens


  Signaling molecules that influence cell fate in a concentration-dependent manner
• Signaling mechanisms


  1. Phosphorylation

  2. GTP binding

  
• Mutations in signaling pathways

  Can produce oncogenes with uncontrolled signaling

  
• Gene regulation occurs at the post-translational level

  
• Molecular chaperones


  Assist protein folding to the correct and most stable form

  
• Molecular chaperones


  • Heat shock proteins (hsps)
• Misfolded proteins are degraded by proteasomes
• Proteasomes


  Abundant sites for protein degradation, with protease activity isolated inside a hollow cylinder

  
• Proteins can be marked for proteasomal degradation by addition of a polyubiquitin chain

  
• Ubiquitin


  A small protein that can be covalently added to different sites on proteins by ubiquitin ligases to regulate their function

  
• Regulation of protein degradation

  1. Signals activate ubiquitin ligase complexes

  2. Ubiquitinated proteins are sent to the proteasome for degradation

  
• Post-translational modifications allow rapid changes in protein activity, localization, and stability
• Signaling pathways are interconnected and can branch out to impact many cell functions
• Endocrine, paracrine, and juxtacrine signaling

  Types of intercellular communication
• Nuclear receptors


  Transcription factors that translocate to the nucleus upon ligand binding
• Receptors expressed and signals received determine cell function
• Integrins


  Transmembrane proteins that help cells adhere to the extracellular matrix and transmit signals
• Anoikis is apoptosis due to loss of integrin-mediated cell adhesion
• Mammary epithelial cells


  • Extracellular matrix signals direct normal structure and function
• Signaling responses can be "fast" (protein modification) or "slow" (gene expression)

  
• Positive and negative feedback in signaling pathways


  Shapes the duration and dynamics of signaling
• GTPases


  Molecular switches in signaling pathways, with GTP-bound form being active
• Kinases and phosphatases


  Enzymes that add and remove phosphate groups, creating molecular switches
• Mutations affecting GTPase or kinase signaling are common in cancer and can create oncogenes