Two classical examples of cme are ironbound transferrin. 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. The dynamin gtpase forms a polymerize collar around the endocytic neck and mediates. 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. What are endocytosis, pinocytosis and phagocytosis. Movie 2 clathrinmediated endocytosis in vivo on vimeo. Clathrin mediated endocytosis is mediated by the production of small approx. The clathrin independent pathways are further classified as 1 caveolae mediated endocytosis, 2 clathrin and caveolaeindependent endocytosis and 3 macropinocytosis. Baoliang song and colleagues report that the clathrin adaptor numb recognizes a peptide motif within the cholesterol transporter npc1l1.
Eh 1 domaincontaining proteins are a growing family of adaptor proteins that play an integral role in clathrin mediated endocytosis. 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. During clathrin mediated endocytosis cme, the phosphoinositide phosphatidylinositol4,5bisphosphate ptdins4,5p 2. 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. We discuss the wellstudied clathrin mediated endocytic mechanisms and dissect endocytic pathways that proceed. Several different forms of endocytosis are present in vivo including phagocytosis, macropinocytosis, caveoli mediated endocytosis, and clathrin mediated endocytosis cme doherty and mcmahon, 2009. 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. Dynamics of ccps and ccvs over 15 min at 10 sec intervals in a 75 x 99 x 40. 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. Clathrin mediated endocytosis by janet iwasa and tom. Despite enormous recent progress toward understanding biophysical aspects of arrestin function 4,5, its cell biology remains relatively poorly understood. Clathrin mediated endocytosis and degradation youtube.
These are referred to as clathrin independent endocytosis cie. Clathrinmediated endocytosis cme is the bestcharacterized mechanism governing cellular membrane and protein trafficking. Receptor mediated endocytosis of ldl cholesterol dnatube. One wellcharacterized example of receptor mediated endocytosis is the transport of lowdensity lipoproteins ldl cholesterol into the cell. Cme is a rapid and highly dynamic event mediated by the cumulative effect of many spatially and temporally separate individual events. 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. Clathrin mediated endocytosis cme is the major pathway for internalization of membrane proteins from the cell surface. 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.
Join our mailing list oupblog twitter facebook youtube tumblr. Clathrin mediated endocytosis is a modular process that involves core and accessory adaptor proteins that package cargoes into vesicles, ultimately leading to their uptake. The membrane of the fused vesicles then diffuses laterally to the areas outside the active zone where it is retrieved by clathrinmediated endocytosis. Viral protein involved in virus internalization by the host cell via clathrin mediated endocytosis. Selection of transmembrane proteins referred to as cargo for internalization by clathrin mediated endocytosis involves recognition of endocytic signals in the. 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. Clathrin mediated endocytosis cme is the major endocytic pathway in mammalian cells. Reorganization of cellular membranes and transport of components from one lipidbilayer bounded compartment to another determine much of the internal structure of a cell. In neurons, endocytosis can occur within the spine. 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. Ironbound transferrin is bound to its receptor on the exterior cell membrane. Sequential steps in clathrinmediated synaptic vesicle. 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. In this approach pinocytosis is classified as clathrin dependent endocytosis also known as clathrin mediated endocytosis cme and clathrin independent endocytosis.
This mechanism internalizes specific extracellular macromolecules through the binding to and internalization of cell surface receptors. To date, the best characterized pathway is clathrin mediated endocytosis. 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. Realtime analysis of clathrinmediated endocytosis during 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. Clathrin assembly into lattices stabilize the membrane curvature. Talk how cell take in things from the outside by forming vesicles both endosomes or clathrin coated vesicles. The mechanism by which cells regulate clathrin mediated endocytosis of ironbound tf was viewed as a constitutive process that occurs continuously without regulatory constraints. Clathrin mediated endocytosis of virus by host clathrin mediated endoycytosis cme is triggered by the binding of the virion to host receptors. Clathrin s role as a scaffold but not in receptor endocytosis is required for akt 308 phosphorylation upon epidermal growth factor stimulation 12, 27. Ultrafast endocytosis at mouse hippocampal synapses. Clathrinmediated endocytosis of virus by host viralzone page.
The effects of mortalin and clathrin mediated endocytosis on pedv entry in ipecj2 cells. 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. Clathrin mediated endoycytosis cme is triggered by the binding of the virion to host receptors. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Endocytic pathways constitute an evolutionarily ancient system that significantly contributed to. Clathrin definition of clathrin by medical dictionary. The clathrin adaptor numb regulates intestinal cholesterol. In fact, clathrin is most abundantly expressed in the central nervous system, where it is found to be particularly concentrated in presynaptic nerve terminals. It should be noted that clathrin independent endocytosis can occur even when the cholesterol level in the membrane has.
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. Eukaryotic cells use multiple pathways for the endocytic entry of proteins and lipids at the plasma membrane. 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. This video discusses receptor mediated endocytosis in relation to low density lipoprotein ldl synthesis. Endocytosis is a fundamental cellular process in all eukaryotic cells. Dynamics of clathrinmediated endocytosis and its requirement for. 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. 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. Realtime analysis of clathrinmediated endocytosis during. 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.
Phagocytosis is the engulfment of large extracellular particles above about a micron, and is used by macrophages to recognize, engulf and degrade. Clathrinmediated endocytosis is mediated by the production of small approx. 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. Abstractmacromolecules gain access to the cytoplasm of eukaryotic cells using one of several ways of which. The last two types of endocytosis are slightly more specialized, and require different cellular technology to occur. Disruption of endocytosis through chemical inhibition of. This suggests that the contents of the cargo within each clathrincoated pit might not be identical. Clathrin mediated endocytosis and the endocytic pathway part 1 duration. In mdck cells, which endogenously express dynamin2, the dynamin2egfp fluorescence demonstrated identical spatial and temporal. Clathrin mediated endocytosis cme is the major pathway of epidermal growth factor receptor egfr internalization. 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. 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. Figure 3 intracellular fate of clathrin mediated endocytosis.
Adaptorprotein complexes are key components of this pathway that bind directly to clathrin,other endocytic regulatory. In this video we discuss the clathrin mediated endocytosis pathway by which we produce endocytic vesicles and also the endocytic pathway. Clathrin is a coat protein on the pits with a bristlelike action. Clathrin is a coat protein that has been shown to function in receptor mediated endocytosis events at the plasma membrane.
Cell biology tutorial explaining the process of endocytosis in clatherincoated vesicles and the maturation of endosomes. Clathrinmediated endocytosis cme is a universal internalization route in eukaryotes samaj et al. Monitoring clathrinmediated endocytosis during synaptic. This animation, completed in collaboration with tomas kirchhausen harvard medical school, shows clathrin mediated endocytosis.
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. Transmembrane proteins targeted for internalization associate with components of the endocytic machinery, predominantly with subunits of clathrin adaptor complexes, such. Lessons from yeast for clathrinmediated endocytosis. Ldl binds to transmembrane receptors on the cell membrane. Mortalin restricts porcine epidemic diarrhea virus entry. Clathrin mediated endocytosis and its role in viral entry. Clathrin is a coat protein that has been shown to function in receptormediated endocytosis events at the plasma membrane. 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. Intersectin, an adaptor protein involved in clathrinmediated. Boston college cell biology extra credit project by john mcginty, katherine murphy, and jacqueline figueredo.
Donaldson3 1national centre for biological sciences, tata institute of fundamental research, and institute for stem cell biologyand regenerative medicine, bangalore 560065, india. Aug 21, 2009 receptor mediated endocytosis is a distinct type of endocytosis in animal cells. Clathrinmediated endocytosis of virus by host viralzone. However, cme may be too slow to internalize proteins from the cell surface during certain physiological processes such as reaction. Synaptic vesicles are regenerated directly from the plasma membrane in the absence of ultrafast endocytosis. Clathrin independent pathways of endocytosis satyajit mayor1, robert g. This chapter presents an overview of the mechanisms of clathrin mediated endocytosis and how itis regulated. The architects dietrich and untertrifaller created a rustic, alpine atmosphere without overwhelming the. Clathrin was first purified by barbara pearse more than 30 years ago, using coated vesicles isolated from pig brain. 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. 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. The virion attachment to the host receptor induces the binding of an adaptor protein to the receptor cytoplasmic tail. Therefore, a fast mode of endocytosis is either clathrin independent or involves preassembled easily retrievable clathrin lattices at sites of endocytosis.
Clathrindependent endocytosis is required for immunity. In clathrin mediated endocytosis, larger macromolecules are taken into a cell through concentrated areas of clathrin coated vesicles. Schmid, alexander sorkin, and marino zerial molecular structure, function, and dynamics of clathrin mediated membrane traffic tom kirchhausen, david owen, and stephen c. One of the beststudied examples of receptor mediated endocytosis is the uptake of cholesterol from the extracellular fluid.
Pdf difference between endocytosis and phagocytosis. Cme occurs via the assembly and maturation of clathrin coated pits that concentrate cargo as they. Key events in synaptic vesicle endocytosis intechopen. Intracellular compartments exocytosis, endocytosis, and the. Phosphatidylinositol control of endocytosis nature cell. Evolutionary changes on the way to clathrinmediated endocytosis. Feel free to download and use for teaching purposes. Colocalization of less than 100% is consistent with observations of clathrin and ap2 in mammalian cells rappoport et al. 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. In clathrin mediated endocytosis, clathrin is recruited from the cytosol into the inner leaflet of the cell membrane to form the clathrin coated pit. Clathrin mediated endocytosis and the endocytic pathway part 8 duration. These observations indicate that clathrin mediated endocytosis is the major, if not exclusive, mechanism of retrieval in small hippocampal synapses. Clathrin mediated endocytosis is the most common type of endocytosis clathrin builds a coat around the budding membrane and an actin. Harrison endocytic accessory factors and regulation of clathrin mediated endocytosis christien j.
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. The animation below shows the process of clathrin mediated endocytosis. Endocytic mechanisms control the lipid and protein composition of the plasma membrane, thereby regulating how cells interact with their environments. Segmented cells reveal brighter clathrin puncta at the vascular endothelium than at muscle fibers c. Visualizing clathrinmediated endocytosis of g protein. 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. Molecular mechanism and physiological functions of clathrin. Coated pits, coated vesicles, and receptormediated endocytosis. Cargo recognition in clathrin mediated endocytosis. Clathrinmediated endocytosis regulates fmlpmediated. This animation, completed in collaboration with tomas kirchhausen harvard medical school, shows clathrinmediated endocytosis. Clathrin is considered the prototype vesicle coat protein whose selfassembly mediates sorting of membrane cargo and recruitment of lipid modifiers. 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. 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. All the above results further indicated that mortalin decreased pedv entry by downregulating clathrin mediated endocytosis, both in vero and ipecj2 cells. 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. The best estimates for the speed of clathrin mediated endocytosis at the synapse come from vesicle proteins tagged with phlourin. Endocytosis, phagocytosis, and pinocytosis video khan. Molecular mechanism and physiological functions of. Adapter proteins allow clathrin to attach to the inner surface of the 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. Clathrin regenerates synaptic vesicles from endosomes. 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. As clathrin mediated endocytosis is rate limited, it cannot maintain endocytosis to large stimulation, so another method is required.
Clathrinadaptor ratio and membrane tension regulate the. Clathrin coated vesicles ccvs are found in virtually all cells and form domains of the plasma membrane termed clathrin coated pits. Following ko, there is no endocytosis with mild stimulation. It is commonly believed that cme mediates longterm attenuation of egfr signaling by targeting the receptor for degradation. To date, the best characterized pathway is 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. Third, vesicle fusion is associated with the movement of clathrin and vesicle proteins out of the synapse into the neighbouring axon. Clathrinmediated endocytosis this animation shows the process of clathrinmediated endocytosis of transferrin receptors, focusing on the assembly and disassembly of the clathrin cage.