7 Interactions Between Cells and Their Environment Flashcards
Glycocalyx
- Structure
- 4 Functions
- Formed from carb projection from MB
1. Mediates cell-cell and cell-substratum interxns
2. Mechanical protection
3. Barrier against some MLCs
4. Binds regulatory MLCs
Extracellular Matrix (ECM)
- Structure
- 1 Function
- An organized network beyond the MB
- regulatory role: determines cell shape and activities through physical and biochemical signalling
Basement Membrane (Animal)
- Structure
- 5 Functions
- A specialized ECM - a continuous sheet that underlies epithelial tissue and surrounds blood vessels
1. Maintain cell attachment
2. Serves as substratum for cell migration
3. Barrier to macroMLCs
4. Establish epithelial cell polarity
5. Prevents cell death
3 Features of ECM Proteins
- Typically long, fribrous
- Secreted by cells into ECM
- Capable of self-assembling into 3D network
Collagen I
- Structure
- 1 Function
- 3 alpha helices wound around each other
- Provide high tensile strength (determines the mechanical property of ECM)
Proteoglycan Complex
- Structure
- 3 Functions
- a core protein with GAGs (repeating dissacharide) which are negatively charged, allowing it to form a porous, hydrated gel
1. Resist compression/cushion cells
2. Provide binding sites for growth hormones to protect from proteases
3. Regulate diffusion of small signalling MLCs in embryo
Firbonectin (Fn)
- Structure
- 1 Function
- a linear array of distinct polypeptides (Fn modules) containing binding sites that are revealed under pulling
- Guides migrating cells during embryo development
Laminins
- Structure
- 3 Functions
- 3 polypeptide chains linked by disulfide bonds
1. Help cell migration during development
2. Lines the basement membrane in a network
3. Contains domains for interaction
How is the ECM dynamic?
- can be stretched
- constantly remodeling by degradation (by MMPs), cross linking, and reconstruction
Cellular Mechanotransduction
-Definition
-Process by which mechanical forces on the surface is converted by focal adhesions into biochemical signals in the cytoplasm
Focal Adhesion
- Structure
- 1 Function
- sites for cells to adhere to their substratum
- send signals to the cell interior
Integrins
- Structure
- 2 Functions
- membrane protein composed of heterodimers with alpha and beta subunits
1. Integrate extra and intra cellular environments
2. Linkage between integrins and their ligands mediates adhesion of cells to substratum or other cells
Binding of proteins to integrins is facilitated by ___
RGD (a tripeptide)
Describe the process of Inside-out Signalling
- Talin binds to the tails of integrin on cytoplasmic side
2. This induces conformational change in integrin, allowing to bind to ligands in the ECM
Describe the process of Outside-in Signalling
- A ligand binds to the extracellular domain of an integrin
- This induces conformational change at the cytoplasmic end
- The shape change can:
a) Allow talin to bind thereby engaging the actin cytoskeleton
OR
b) Initiate a cascade of signals by inducing protein phosphorylation that ultimately changes gene expression thereby changing the cell behaviour
Hemidesmosomes
- Structure
- 1 Function
- an attachment of epithelial cells to the basement membrane
- involved in adhesion to substratum
Cell-cell recognition is essential to establishing and maintaining ___ as proved by ____ (experiment)
Tissue organization, Cell mixing studies in embryos
Which four families of integral membrane proteins play a major role in mediating cell-cell adhesion?
- Selectins
- Some members of Immunoglobulin superfamily (IgSF)
- Some members of the Integrin family
- Cadherins
Selectins
- Structure
- 1 Function
- integral membrane glycoprotein with a small, cytoplasmic domain, a single membrane-spanning domain, and a large extracellular domain
- binds to sugars on the surface of cells mediating cell-cell adhesion
Immunoglobulin Superfamily (IgSF) -1 Function
-mediates cell-cell adhesion in immune functions
Describe inflammatory response from the perspective of an immune cell (probably don’t need to know)
-5 steps
- Leukocytes move to site of injury
- Neutrophoils attach to selectins
- Neutrophils roll along wall of vessel. As neutrophils interact with inflamed venule endothelium, platelet activating factor (PAF) is displayed
- PAF sends a signal to increase binding activity of some integrins via inside-out signalling
- Activated integrins cause neutrophils to stop rolling and adhere to wall of vessel via IgSF receptors
Cadherins
- Structure
- 1 Function
- glycroprotein
- mediate Ca2+-dependent cell-cell adhesion; cadherins join cells of similar types by preferentially binding to the same cadherin at the surface of the neighbouring cell
Epithelial-mesenchymal Transition (EMT)
- Structure
- 1 Function
- formed by cadherins
- involved in mediating adhesive contact during embryo development, tissue regeneration, and metastasis of cancer
What are 3 special properties of metastatic cells in terms of cell adhesion?
- Less adhesive
- Able to penetrate several barriers
- Able to invade normal tissues
What contributes to metastasis of tumor cells?
The loss of cadherin and other types of cell-adhesion molecules during tumor growth.
Integrins and cadherins can both transmit signals from ___ to ___
extracellular environment, cytoplasm
What are the 4 types of intercellular junction complexes?
- Adherens junction
- Tight junction
- Desmosome
- Gap junction
Adherens junctions and desmosomes ___ (function)
anchor cells to other cells using adherins
Tight junction
- what it is
- 3 Functions
- specialized contact between epithelial cells
1. Barrier to free diffusion of water and solutes from extracellular compartment
2. Block membrane protein diffusion
3. Permeable to specific ions and solutes
Gap junction
- Structure
- 5 Features
- sites between animal cells, composed of membrane protein connexins which organize into connexons
1. Mediates intercellular communication
2. Allows diffusion of low weight molecules
3. Can be open or close in response to Ca2+ concentration
4. Allows integration of activities of individual cells into a functional unit
5. Communication between different cells determined by compatibility between connexins
Tunneling Nanotubes
-what is it
A type of cell-cell communication involving a thin tube capable of carrying tiny particles between the cytoplasm of neighboring cells
