Endocytosis is a cellular process in which substances are brought into the cell. One cell can send a molecule over to another cell, and a receptor protein in the cell membrane will receive it, just like molecular walkietalkies. This animation, completed in collaboration with tomas kirchhausen harvard medical school, shows clathrin mediated endocytosis. Clathrin is considered the prototype vesicle coat protein whose selfassembly mediates sorting of membrane cargo and recruitment of lipid modifiers. Evolutionary changes on the way to clathrinmediated endocytosis. Donaldson3 1national centre for biological sciences, tata institute of fundamental research, and institute for stem cell biologyand regenerative medicine, bangalore 560065, india. Disruption of endocytosis through chemical inhibition of. Eh 1 domaincontaining proteins are a growing family of adaptor proteins that play an integral role in clathrin mediated endocytosis. These are referred to as clathrin independent endocytosis cie. Synaptic vesicles are regenerated directly from the plasma membrane in the absence of ultrafast endocytosis.
Following ko, there is no endocytosis with mild stimulation. Ironbound transferrin is bound to its receptor on the exterior cell membrane. We discuss the wellstudied clathrin mediated endocytic mechanisms and dissect endocytic pathways that proceed. All the above results further indicated that mortalin decreased pedv entry by downregulating clathrin mediated endocytosis, both in vero and ipecj2 cells. Receptor mediated endocytosis of ldl cholesterol dnatube.
Pinocytosis is further segregated into the pathways macropinocytosis, clathrin mediated endocytosis, caveolin mediated endocytosis, or clathrin and caveolinindependent endocytosis, all of which differ by the mechanism of vesicle formation as well as the resulting size of these vesicles. Ultrafast endocytosis at mouse hippocampal synapses. Clathrin mediated endocytosis cme is an essential uptake pathway that relocates membrane or extracellular cargo into the cell to regulate multiple cellular functions and cell homeostasis 1. Coated pits, coated vesicles, and receptormediated endocytosis. The dynamin gtpase forms a polymerize collar around the endocytic neck and mediates. Clathrin mediated endocytosis is mediated by the production of small approx. Clathrin definition of clathrin by medical dictionary. This mechanism internalizes specific extracellular macromolecules through the binding to and internalization of cell surface receptors. Phagocytosis is the engulfment of large extracellular particles above about a micron, and is used by macrophages to recognize, engulf and degrade. Molecular mechanism and physiological functions of clathrin. Join our mailing list oupblog twitter facebook youtube tumblr. Clathrin s role as a scaffold but not in receptor endocytosis is required for akt 308 phosphorylation upon epidermal growth factor stimulation 12, 27. Transmembrane proteins targeted for internalization associate with components of the endocytic machinery, predominantly with subunits of clathrin adaptor complexes, such as ap2, ap180, or clathrin assembly lymphoid myeloid. Colocalization of less than 100% is consistent with observations of clathrin and ap2 in mammalian cells rappoport et al.
Clathrin mediated endocytosis box 4,which is responsible for the internalization of nutrients,pathogens,antigens,growth factors and receptors,is the most wellcharacterized mechanism for the entry of molecules into cells. Selection of transmembrane proteins referred to as cargo for internalization by clathrin mediated endocytosis involves recognition of endocytic signals in the. What are endocytosis, pinocytosis and phagocytosis. The animation below shows the process of clathrin mediated endocytosis. Clathrin independent pathways of endocytosis satyajit mayor1, robert g. Realtime analysis of clathrinmediated endocytosis during cell. Synaptic vesicle proteins freshly added to the surface after a single action potential are recycled with a time constant of about 1520 s 32,33. Dec 16, 2010 clathrin mediated endocytosis this animation shows the process of clathrin mediated endocytosis of transferrin receptors, focusing on the assembly and disassembly of the clathrin cage. Clathrindependent endocytosis is required for immunity. Sequential steps in clathrinmediated synaptic vesicle endocytosis brodin, low and shupliakov 3 phosphoinositide synthesis can enhance coat formation 20, while capping of phosphoinositides by overexpressing phosphoinositidebinding proteins has an inhibitory effect 21. Adapter proteins allow clathrin to attach to the inner surface of the membrane. This animation, completed in collaboration with tomas kirchhausen harvard medical school, shows clathrinmediated endocytosis.
The pit then is pinched off, to form a clathrin coated vesicle that then begins to lose its clathrin coat in the cytosol. Ldl binds to transmembrane receptors on the cell membrane. Clathrin is a coat protein that has been shown to function in receptor mediated endocytosis events at the plasma membrane. Clathrin mediated endocytosis cme is a highly conserved and essential cellular process in eukaryotic cells, but its dynamic and vital nature makes it challenging to study using classical. During clathrin mediated endocytosis cme, the phosphoinositide phosphatidylinositol4,5bisphosphate ptdins4,5p 2. Viral protein involved in virus internalization by the host cell via clathrin mediated endocytosis. Simultaneous dualcolor totalinternalreflection fluorescence microscopy tirfm was performed to analyze the internalization and distribution of markers for clathrin mediated endocytosis clathrin, dynamin1, dynamin2 and transferrin in migrating cells. The ability to internalize material from outside the cell is important for several cellular processes including the ingestion of essential nutrients, removal of dead or damaged cells from the body, and defense against microorganisms. In neurons, endocytosis can occur within the spine. Mortalin restricts porcine epidemic diarrhea virus entry. Baoliang song and colleagues report that the clathrin adaptor numb recognizes a peptide motif within the cholesterol transporter npc1l1. Endocytosis, phagocytosis, and pinocytosis video khan. Clathrin mediated endoycytosis cme is triggered by the binding of the virion to host receptors.
This process forms vesicles containing the absorbed substances and is strictly mediated by receptors on the surface of the cell. Pdf difference between endocytosis and phagocytosis. Abstractmacromolecules gain access to the cytoplasm of eukaryotic cells using one of several ways of which. These observations indicate that clathrin mediated endocytosis is the major, if not exclusive, mechanism of retrieval in small hippocampal synapses. Clathrin mediated endocytosis and its role in viral entry. Receptormediated endocytosis rme, also called clathrinmediated endocytosis, is a process by which cells absorb metabolites, hormones, proteins and in some cases viruses by the inward budding of the plasma membrane invagination. Movie 2 clathrinmediated endocytosis in vivo on vimeo. It should be noted that clathrin independent endocytosis can occur even when the cholesterol level in the membrane has. The process of membrane budding to form a vesicle is generally mediated by a protein coat, which acts both as a means to deform the membrane and to concentrate specific types of proteins inside the nascent vesicle. Feel free to download and use for teaching purposes. Clathrin mediated endocytosis of virus by host clathrin mediated endoycytosis cme is triggered by the binding of the virion to host receptors. The internalization of a subset of plasma membrane proteins by clathrin mediated endocytosis is one the bestcharacterized sorting processes that takes place in the endomembrane system of eukaryotic cells kirchhausen 2014. Molecular mechanism and physiological functions of. In clathrin mediated endocytosis, larger macromolecules are taken into a cell through concentrated areas of clathrin coated vesicles.
Endocytic mechanisms control the lipid and protein composition of the plasma membrane, thereby regulating how cells interact with their environments. Cme is a rapid and highly dynamic event mediated by the cumulative effect of many spatially and temporally separate individual events. Talk how cell take in things from the outside by forming vesicles both endosomes or clathrin coated vesicles. Clathrin coated vesicles ccvs are found in virtually all cells and form domains of the plasma membrane termed clathrin coated pits. Dynamics of clathrinmediated endocytosis and its requirement for. Cell biology tutorial explaining the process of endocytosis in clatherincoated vesicles and the maturation of endosomes. In response to an internalization signal, clathrin is assembled on the inside face of the cell membrane to form characteristic invaginations or clathrin coated pits that pinch off through the action of dnm1dynamin1 or dnm2dynamin2. Intersectin, an adaptor protein involved in clathrinmediated. Clathrin was first purified by barbara pearse more than 30 years ago, using coated vesicles isolated from pig brain.
Clathrin mediated endocytosis is the most common type of endocytosis clathrin builds a coat around the budding membrane and an actin. However, cme may be too slow to internalize proteins from the cell surface during certain physiological processes such as reaction. Clathrin mediated endocytosis cme is the major endocytic pathway in mammalian cells. Cme occurs via the assembly and maturation of clathrin coated pits that concentrate cargo as they. Clathrin assembly into lattices stabilize the membrane curvature. Molecular movie representing the assembly of a clathrin coated pit, its dynaminbased budding to form a coated vesicle and the removal of the coat mediated by the uncoating hsc70auxilin dependent. Detailed knowledge of clathrin biochemistry, structure, and interacting proteins has accumulated since the first observation, almost 50 years ago, of its role in receptor mediated endocytosis of yolk protein. Endocytosis can however take place in response to large stimulation. It describes how the cholesterol molecules are transported through the cell membrane with the help of adaptin and clathrin to be delivered to the endosome.
Key events in synaptic vesicle endocytosis intechopen. Endocytic pathways constitute an evolutionarily ancient system that significantly contributed to. The clathrin adaptor numb regulates intestinal cholesterol. The architects dietrich and untertrifaller created a rustic, alpine atmosphere without overwhelming the. Several different forms of endocytosis are present in vivo including phagocytosis, macropinocytosis, caveoli mediated endocytosis, and clathrin mediated endocytosis cme doherty and mcmahon, 2009. Clathrin dependent endocytosis is required for immunity mediated by pattern recognition receptor kinases malick mbengue a, gildas bourdais a, fabio gervasi a, b, martina beck a, ji zhou. Fluorescent gm1, normally internalized by clathrin independent endocytosis in hela cells with low cav1, was induced to partially internalize via the clathrin pathway in the presence of ctxb. Clathrinadaptor ratio and membrane tension regulate the. Clathrin regenerates synaptic vesicles from endosomes. The best estimates for the speed of clathrin mediated endocytosis at the synapse come from vesicle proteins tagged with phlourin. Cargo recognition in clathrin mediated endocytosis. Visualizing clathrinmediated endocytosis of g protein. A longlasting delay preceding the fluorescent transients shows that endocytosis during the first few seconds of continuing stimulation cannot be mediated by newly formed clathrin coated pits.
Therefore, a fast mode of endocytosis is either clathrin independent or involves preassembled easily retrievable clathrin lattices at sites of endocytosis. This suggests that the contents of the cargo within each clathrincoated pit might not be identical. Clathrin mediated endocytosis cme is the major pathway for internalization of membrane proteins from the cell surface. This video describes the concept behind clathrinmediated endocytosis. The architects dietrich and untertrifaller created a rustic, alpine atmosphere without overwhelming the guests with kitsch. Two classical examples of cme are ironbound transferrin. Clathrinmediated endocytosis regulates fmlpmediated. Clathrinmediated endocytosis cme is the bestcharacterized mechanism governing cellular membrane and protein trafficking. Nov 25, 2014 in this video we discuss the clathrin mediated endocytosis pathway by which we produce endocytic vesicles and also the endocytic pathway which follows. Segmented cells reveal brighter clathrin puncta at the vascular endothelium than at muscle fibers c. Here we describe the use of tirfm to visualize clathrin mediated endocytosis cme at the level of individual ccps in living cells in real time.
Schmid, alexander sorkin, and marino zerial molecular structure, function, and dynamics of clathrin mediated membrane traffic tom kirchhausen, david owen, and stephen c. Clathrin is a coat protein that has been shown to function in receptormediated endocytosis events at the plasma membrane. This video discusses receptor mediated endocytosis in relation to low density lipoprotein ldl synthesis. The virion attachment to the host receptor induces the binding of an adaptor protein to the receptor cytoplasmic tail. The membrane of the fused vesicles then diffuses laterally to the areas outside the active zone where it is retrieved by clathrinmediated endocytosis. Adaptorprotein complexes are key components of this pathway that bind directly to clathrin,other endocytic regulatory. In clathrin mediated endocytosis, clathrin is recruited from the cytosol into the inner leaflet of the cell membrane to form the clathrin coated pit. The clathrin independent pathways are further classified as 1 caveolae mediated endocytosis, 2 clathrin and caveolaeindependent endocytosis and 3 macropinocytosis.
Clathrinmediated endocytosis of virus by host viralzone. Endocytosis is a fundamental cellular process in all eukaryotic cells. Jul 22, 2011 clathrin mediated endocytosis is a modular process that involves core and accessory adaptor proteins that package cargoes into vesicles, ultimately leading to their uptake. Clathrinmediated endocytosis this animation shows the process of clathrinmediated endocytosis of transferrin receptors, focusing on the assembly and disassembly of the clathrin cage. Harrison endocytic accessory factors and regulation of clathrin mediated endocytosis christien j. Realtime analysis of clathrinmediated endocytosis during. Receptor mediated endocytosis rme, also called clathrin mediated endocytosis, is a process by which cells absorb metabolites, hormones, proteins and in some cases viruses by the inward budding of the plasma membrane invagination. Dynamics of ccps and ccvs over 15 min at 10 sec intervals in a 75 x 99 x 40. Clathrin mediated endocytosis is a modular process that involves core and accessory adaptor proteins that package cargoes into vesicles, ultimately leading to their uptake. It is commonly believed that cme mediates longterm attenuation of egfr signaling by targeting the receptor for degradation.
Lessons from yeast for clathrinmediated endocytosis. Despite enormous recent progress toward understanding biophysical aspects of arrestin function 4,5, its cell biology remains relatively poorly understood. One wellcharacterized example of receptor mediated endocytosis is the transport of lowdensity lipoproteins ldl cholesterol into the cell. Clathrincoated vesicle formation involves several morphologically distinct steps, from clathrin coat binding, invagination of the coated bud, constriction and fission of the pit neck and. This chapter presents an overview of the mechanisms of clathrinmediated endocytosis and how itis regulated.
Monitoring clathrinmediated endocytosis during synaptic. One of the beststudied examples of receptor mediated endocytosis is the uptake of cholesterol from the extracellular fluid. The effects of mortalin and clathrin mediated endocytosis on pedv entry in ipecj2 cells. Aug 21, 2009 receptor mediated endocytosis is a distinct type of endocytosis in animal cells. Boston college cell biology extra credit project by john mcginty, katherine murphy, and jacqueline figueredo. With the advent of new molecular genetic and imaging tools, an understanding of the different ways by which a cell may endocytose cargo is increasing by leaps and bounds. As clathrin mediated endocytosis is rate limited, it cannot maintain endocytosis to large stimulation, so another method is required. Reorganization of cellular membranes and transport of components from one lipidbilayer bounded compartment to another determine much of the internal structure of a cell.
Figure 3 intracellular fate of clathrin mediated endocytosis. Learn vocabulary, terms, and more with flashcards, games, and other study tools. In mdck cells, which endogenously express dynamin2, the dynamin2egfp fluorescence demonstrated identical spatial and temporal. Transmembrane proteins targeted for internalization associate with components of the endocytic machinery, predominantly with subunits of clathrin adaptor complexes, such. To date, the best characterized pathway is clathrinmediated endocytosis. E glycoprotein is the most important molecule during the viral entry process as it appears to be responsible for receptor recognition and attachment to the cell surface, triggering the clathrin mediated endocytosis and the subsequent fusion of viral and cellular membranes.
Clathrin is a coat protein on the pits with a bristlelike action. This chapter presents an overview of the mechanisms of clathrin mediated endocytosis and how itis regulated. This video describes the concept behind clathrin mediated endocytosis. Mechanistically, spine endocytosis is likely mediated by both clathrin dependent and clathrin independent pathways, but the bestcharacterized spine endocytic mechanism occurs via clathrin coated vesicles. Clathrin mediated endocytosis cme is the major pathway of epidermal growth factor receptor egfr internalization. Sequential steps in clathrinmediated synaptic vesicle. In this approach pinocytosis is classified as clathrin dependent endocytosis also known as clathrin mediated endocytosis cme and clathrin independent endocytosis. The mechanism by which cells regulate clathrin mediated endocytosis of ironbound tf was viewed as a constitutive process that occurs continuously without regulatory constraints. Clathrinmediated endocytosis of virus by host viralzone page. Phosphatidylinositol control of endocytosis nature cell.
Clathrin mediated endocytosis cme is a vesicular transport event that facilitates the internalization and recycling of receptors engaged in a variety of processes, including signal transduction gprotein and tyrosine kinase receptors, nutrient uptake and synaptic vesicle reformation 11514193. The last two types of endocytosis are slightly more specialized, and require different cellular technology to occur. Clathrin mediated endocytosis and degradation youtube. Clathrinmediated endocytosis cme is a universal internalization route in eukaryotes samaj et al. Clathrindependent endocytosis is required for immunity mediated by pattern recognition receptor kinases malick mbenguea,1,2, gildas bourdaisa,1, fabio gervasia,b, martina becka,2, ji zhou. Eukaryotic cells use multiple pathways for the endocytic entry of proteins and lipids at the plasma membrane. Third, vesicle fusion is associated with the movement of clathrin and vesicle proteins out of the synapse into the neighbouring axon. In this video we discuss the clathrin mediated endocytosis pathway by which we produce endocytic vesicles and also the endocytic pathway. In fact, clathrin is most abundantly expressed in the central nervous system, where it is found to be particularly concentrated in presynaptic nerve terminals. Intracellular compartments exocytosis, endocytosis, and the. Jan 12, 2008 today it is generally accepted that there are several endocytic mechanisms, both the clathrin dependent one and mechanisms which operate without clathrin and with different requirements when it comes to dynamin, small gtpbinding proteins of the rho family and specific lipids.
It is responsible for the uptake of transmembrane receptors and transporters, for remodeling plasma membrane composition in response to environmental changes, and for regulating cell surface signaling. Receptor mediated endocytosis had been thought to be assisted by specific proteins, either clathrin or caveolin, polymerizing into a spherical shell around the invagination 3. To date, the best characterized pathway is clathrin mediated endocytosis. Jul 01, 2016 valwood changed the title difference between clatrinmediated and receptor mediated difference between clathrinmediated and receptor mediated jan 16, 2017 sign up for free to join this conversation on github. This idea was first suggested by the finding that mutations in the yeast eh domaincontaining proteins pan1p and end3p have profound effects on endocytosis 1, 2.