Intro to Intra- and Inter-Cell Communication Flashcards
What is the structural and functional difference between an adherens junction and a gap junction?
- adherens junctions: governs cell-cell adhesion. typically localized basal to TJs. comprozed of cadherin-catenin complexes. provide mechanical stability to tissues by connecting adjacent cells. They contribute to cell–cell adhesion, maintaining tissue integrity.
-gap junctions: intercellular communication channels that permit cell to cell passages of small moleules. formed by channel-forming proteins (connexins and innexins). are assembled head-to-head to form homomeric or heteromeric hexmer called connexons. connexons on adjacent cell mebrane –> intercellular gap junction. perform intercellular communication by allowing the passage of ions and small molecules directly between adjacent cells.They play a crucial role in the synchronization of cellular activities, enabling coordinated responses in tissues like the heart, where electrical signals must be rapidly transmitted between cells.
How do adjacent cells communicate?
- paracrine signalling: ligand secreated locally and bind on NEARBY/ADJACENT CELLS
- signalling via plasma membrane-attached proteins: both ligan and receptor are transmebrane proteins, signalling occurs in adjacent cells.
- more than one of these signalling pathways is occuring at the same time
How do distant cells communicate?
- endocrine signalling: hormones secreted in the blood stream act receptors at DISTANT SITES
- more than one of these signalling pathways is occuring at the same time
What is a G protein? Why are they important to proper cell function?
- Guanosine nucleotide binding protein (binds GTP and GDP)
- have intrinsic GTPase activity; can be accelerated by other enzymes (GTPase accerarating proteins (GAPs))
- acts a molecular “ON/OFF” switches; state depends on whether GTP (on) or GDP (off) is bound
- both G protein and GTPase works as switch bc protein is the enzyme
- two types: heterotrimeric G-proteins (large) and momomeric G-proteins (small)
- heterotrimeric G-proteins: formed of 3 subunits (aplha, beta, and gamma). become activated (exchange GDP for GTP in response to activiation of associated g-protein coupled receptors
- G proteins are crucial for cell communication, acting as molecular switches that transmit signals from the cell surface to the inside. They play a key role in regulating various cellular processes, including growth, metabolism, and sensory perception, making them essential for proper cell function and overall physiological balance.
How are G proteins important to the study of drugs and drug effects?
- G proteins are like cellular switches that drugs can fine-tune, making them essential in exploring new therapeutic interventions.
- Many drugs target G protein-coupled receptors (GPCRs), which interact with G proteins. GPCRs are one of the largest and most important families of drug targets. By modulating GPCR-G protein interactions, drugs can influence cellular signaling pathways and physiological responses.
What is a signal transduction system? How are they important in cell-cell interactions?
- a set of molecular events that transmit signals from the exterior to the interior of a cell, leading to a cellular response.
three general stages: - reception: cell recieves an extracellular signal from a signal molecule (could be hormone, transmitter, etc) ; ligand binds to membrane bound receptor. from the extracellular fluid
- transduction: ligand binding elicits a change in the receptor its bound to, resulting in receptor activiation- conformation change and post translation modification- receptor interacts with and activates intercellular singal transducer (signal amplification)
- response: tranducers elecit a particular cell response depending on the signal recieved by the cell; often this results in the expression of gene that coordinate a particlar cell response (cell molitility, prolieration, differentiation, metabolism, etc)
- Signal transduction systems enable cells to communicate with each other.
- By transmitting signals, cells can coordinate responses to external stimuli.
- During development, cells rely on signal transduction systems to guide their differentiation and organization into tissues and organs. aids in homeostasis
- Signal transduction is integral to the immune response
gpcr pathway
see notes
- GPCR pathway is able to transmit extracellular signals to the cell’s interior, leading to various cellular responses. also activates g poteins,
1. binding of hormone incduces a conformational chane in receptor
2. activated receptor bids to alpha G subunit
3. activated receptor casues confromatioal chage in alpha G, troggering dissociated of GDP
4. binding of GTP to aplha G triggers dissociated of G aplha both from the recptor and from beta gamma G
5. hormone dissociates from the receptor; g aplha binds to effector, activating it
6. hydrolysis of GTP and GDP causes aplha G to dissociate from the effector and reassociate with G beta gamma
- the primary transducer in the G pathway is CAMP and trimeric G protein
levels of organization
- organ system : different organs that work togetehr to perform a function
- organ: a collection of tissues that work together to perform a function
- tissue: a collection of cells that work together to perform a particular task
- cells: the basic building blocks of tissues. the instruction manel for their “job”= DNA
do cells float around in an empty “void”?
- no
- extracellular matrix: 3d molecular network formed of water, polysacchardies and proteins. it molecuarly scaffords that holds the cells of tissues together, offers mechanical and elstic support, directs embroyogenesis and tissue morphogenesis, acts as signalling ligans for basolateral cell adhesion molecules, and is a reservior for growth factors.
- connective tissue: loose network of proteins and carbohydrates under epithelial cll layers where fibroblasts are distributed. fibroblasts are connective tissues cell type that secretes ECM components, including collagen and fibronectin. tendon, bone, and cartiliage
- the basal lamina: a specialized ECM found directly underneath epithelial cells. secreted by the same cells that rest atop of it. not produced by fibroblasts. found in cellular tissues
- integrins (anchor in place) interact with eseveral ECM ligands. they form hemidesmosomse and focal contacts. most cells express several integrins, each binding to one type of ligans. functions include: anchoring cells to the basal lamina, promoting motility of migraort cells, and stimulating cell signalling pathways
- cancer cells can grow without being adhered which is why they are so dangerous
how do cells “talk” to eachother to ensure sychronicity and corrdinated function?
-gap junctions
- chemical signalling
- nerve signalling
cadherins: classical, non-classical, protocadherins
-Cadherins are cell adhesion molecules important in forming adherens junctions that let cells adhere to each other.
- classical: linked to actin filaments (so they stay in place). includes epithelial, neural, placental, and vascualr endothelial cadherins. 5 extracellular domains, 1 intracellular domain. both cis and trans insteractions important for cell adhesion
- non-classical: desmosomal caherins (linked to intermediate filaments. good for tissues hat undergo lots of mehanical stress. desmocollins and desmogleins
- protocadherins: largest; typically found in neurons
desmosomes
- button like cell-cell junctions
- mediate adhesion and confer mechanical support (esp. in tissues under high mechanical stress)
-desmosonal cadherins mediate cell-cell adhesions - adaptor proteins form a plaque that anchor desosomal cadherins to the underlying intermediate filament cytoskeletal network
- tight regulation of desmosomes is important
tight junctions
-paracellular pathway
- regulates transports between adjacent cells
- establish polarity because junctions formae are so close. keeps axial stuff in apixial and lateral in lateral
- apixial most junction (closests to microvilli)
- assist in cell dhesion, but primary function is to modulate paracellular permeability (size and charge selective transport of small molecules bewteen cells)
cell polarity
- plasma membrane of polarized cells are organized into at least two discreet regios
- types of junctions that connect cells and help maintain polarity: gap junctions, tight/eperate junctions, anchoring junctions (adherens, desmosomes, and hemidesmosomes)
- polarity is asymmetry in the cell
- has elements to increase surface area
- we need to know this to answer a question about how cells interact
