Cell Junctions Flashcards
What are tissues?
Cells that are closely associated and preform a common or related function
Four types of tissue
Epithelia, connective, muscle, nervous
What is the epithelium
Covering/lining tissue
What does a Gap Junction do?
Mediates cell to cell communication by permitting DIRECT transfer of ions and small molecules by connecting the cytoplasm in adjacent cells
What are Gap Junctions composed of?
Hexamers of integral proteins: connexins and chordates
What type of cells do Gap Junctions connect
Excitable Cells (nerve and muscle)
Where are Gap Junctions found?
Joining virtually all cells in solid tissues
How do Gap Junction isoforms change permeability
Different combinations of connexins
How are Gap Junctions regulated
Changes or signals (neurotransmitters)
How do Tight Junctions hold cells together?
Form a leak-proof intercellular seal by fusing adjacent cell membranes
What determines Tight Junction Permeability?
The tissue it’s found in
What are major aspects of Tight Junctions?
Claudin
Occludin
Zona Occludents
What is Claudin
A main transmembrane protein found within a tight junction that is selectively permeable
Dysregulation of what TJ protien causes cancers and other pathologies? Why?
Claudins.
Impaired barrier function leads to exacerbation of inflammation.
Epidermal growth factors influx contributes to tumorigenesis
How does a pathogenic breach affect claudins?
Creates an overactive inflammatory response and affects claudin expression (they’re sensitive)
What are Anchoring Junctions?
Complexes that adhere cells to other cells or extracellular matrix
Provide strong membrane spanning structure
Types of Anchoring Junctions
Adherens junction
Desmosomes
Hemidesmosomes
Focal adhesion
Adherens Junctions are connected to cytoskeleton by
Actins
How are desmosomes connected to the cytoskeleton?
Intermediate filaments
How are Hemidesmosomes connected to cytoskeleton?
Intermediate filaments
How are Focal Adhesions connected to cytoskeleton?
Actins
How are tight junctions connected to cytoskeleton
Actin
What are Plaque Protiens?
internal Attachment within cell junction
What are Transmembrane proteins?
External Attachment
What is prerequisite to TJ assembly? And where are they located in proximity to TJ.
Formation of Adherens Junctions below.
What determines Cadherin structure? What are some isoforms?
Structure depends on Ca++ ions.
E-cadherin: eipithelial cells
N-cadherin: Nerve, muscle and lens.
P-Cadherin: Placenta and Epidermis
How do Mutations in E-cadehrins cause cancer?
Disrupts the function or production.
Loss of function associated with gain of invasiveness and metastatic potential of cells
Where do Desmosomes play a critical role in the body?
In tissues subjected to mechanical stress such as the myocardium, bladder and skin.
What do Hemidesmosomes and Focal adhesion do?
Aid in the interaction of a cell-extracellular matrix
What do cell junctions do?
Provide mechanical support
Separate cells for protection and traffic regulation
Communication b/w cells
Cell Polarity
