Professor of Cell Biology
Investigator, Howard Hughes Medical Institute
Phone: (203) 737-5207
Lab: (203) 737-4453/-4451
Fax: (203) 737-5246
e-mail: susan.ferronovick@yale.edu Department of Cell Biology
Yale Universtiy School of Medicine
333 Cedar Street
PO Box 208002
New Haven, CT 06520-8002
Vesicle traffic and organelle inheritance
The goal of our research program is to understand how the specificity of vesicle traffic is maintained and how organelles are inherited from mother to daughter cells.
Vesicle Traffic
For our studies on vesicle traffic, we have focused on the multiprotein complex called TRAPP. There are two forms of the TRAPP complex, TRAPP I and TRAPP II. TRAPP I is required for membrane traffic from the endoplasmic reticulum (ER) to the Golgi, while TRAPP II is required for traffic from the early endosome to the Golgi and within the Golgi. Interestingly, spondyloepiphyseal dysplasia tardia, a recessive disorder in bone formation is caused by mutations in the human orthologue of a TRAPP subunit.
Using a vesicle binding assay that employs in vitro formed ER-derived vesicles and pure TRAPP I, we have demonstrated that TRAPP I specifically binds to ER to Golgi vesicles. These findings imply that TRAPP I plays a key role in conferring the specificity of ER to Golgi vesicle traffic. TRAPP I binds to coated ER-derived vesicle via an interaction with the coat cargo adapter complex (see Figure), linking TRAPP I dependent vesicle binding to cargo recognition. Once binding occurs, TRAPP I activates the small GTPase Ypt1p, converting it from its GDP-bound to its GTP-bound form. The activation of Ypt1p by TRAPP I may be the signal that the vesicle has reached its correct acceptor compartment. This then leads to the recruitment of other components, such as Uso1p. The pairing of the SNAREs, a class of membrane proteins that are required for membrane fusion, is the final step in docking an ER-derived vesicle to the Golgi.
Organelle Inheritance
It is the goal of these studies to define the process by which the ER is delivered into daughter cells. To achieve this goal a genetic approach has been used to identify the machinery that moves ER tubules from mother to daughter cells. This approach has led to the identification of a collection of genes whose products are required for ER inheritance. A track and motor that moves ER tubules into daughter cells, as well as a putative receptor for cortical ER in daughter cells have been identified. Orthologues of these components are present in higher cells.
Selected Publications
Cai, H., Reinisch, K. and Ferro-Novick, S. 2007. Coats, Tethers , Rabs and SNAREs work together to mediate the intracellular destination of a transport vesicle. Dev Cell 12: 671-682.
Cai, H., Yu, S., Menon, S., Cai, Y., Lazarova, D., Fu, C., Reinisch, K., Hay, J. C. and Ferro-Novick, S. 2007. TRAPPI tethers COPII vesicles by binding the coat subunit Sec23p. Nature 445: 941-944.
(Commentaries on this paper appeared in Dev Cell and Curr Biol)
Du, Y., Walker, L., Novick, P. and Ferro-Novick, S. 2006. Ptc1p regulates cortical ER inheritance via Slt2p. EMBO J. 25: 4413-4422.
(This paper was highlighted in EMBO J)
Yu, S., Satoh, A., Pypaert, M., Muller, K., Hay, J.C. and Ferro-Novick, S. 2006. mBet3p is required for homotypic COPII vesicle tethering in mammalian cells. J. Cell Biol. 174:359-368.
DeCreane, J.O., Coleman, J., Estrada de Martin, P., Pypaert,M., Anderson, S., Yates III, J.R., Ferro-Novick, S and Novick, P. 2006. Rtn1p is involved in structuring the cortical ER. Mol. Biol. Cell 17:3009-3020.
Cai, H., Zhang, Y., Pypaert, M., Walker, L. and Ferro-Novick, S. 2005. Trs120p mediates traffic from the early endosome to a late Golgi compartment. J. Cell Biol. 171:823-833.
Estrada de Martin,P., Novick,P. and Ferro-Novick,S. 2005. The organization, structure and inheritance of the ER in higher and lower eukaryotes. Biochem. Cell Biol. 83:752-761.
Friday, January 16, 2009
Gunter blobel
http://www.rockefeller.edu/labheads/blobel/blobel-lab.html
John D. Rockefeller, Jr. Professor; Investigator, HHMI
The unidirectional translocation of thousands of distinct proteins across specific intracellular membranes is mediated by "signal" sequences. On average, a signal sequence consists of a stretch of ~15 amino acid residues that is either a transient or permanent part of the protein to be translocated. The signal sequence functions essentially as a ligand. Each signal sequence is membrane specific and is decoded by a complex machinery that is restricted in its location to one particular cellular membrane.
Two distinct mechanisms of translocation have so far been discovered. In one mechanism translocation proceeds through protein conducting channels. The diameter of the aqueous center of these protein conducting channels is limited (~2 nm) so that passage of a protein can proceed only in its unfolded configuration. A number of polypeptide binding proteins assist in keeping the protein to be translocated in an unfolded configuration. Protein conducting channels have recently been detected electrosphysiologically in the endoplasmic reticulum and the prokaryotic plasma membrane. These channels were found to be gated open by the signal sequence. The channel closes after translocation of the chain is completed. In addition to opening and closing across the membrane, the channel must also be able to open and close in a second dimension, namely to the lipid bilayer. This is necessary to permit integration of proteins into membranes. A protein to be integrated into the membrane uses a signal sequence to open the channel. Translocation proceeds until a "stop transfer" sequence of the translocating polypeptide chain interacts with the channel to open it laterally to the lipid bilayer. As a result, the segment of the chain that is located in the channel would be displaced into the bilayer with the channel simultaneously closing in both dimensions. Similar protein conducting channels are likely to exist in the outer as well as the inner membrane of chloroplasts and mitochondria, in the thylakoid membrane of chloroplasts, and in the peroxisomal membrane. The great challenge ahead is to isolate and to characterize these protein conducting channels.
The mechanism of protein translocation across the nuclear pore complex (NPC) is distinct from that of translocation across the above-described protein conducting channels. NPCs are huge organelles (estimated molecular mass: 125 million daltons) that are suspended in 100-nm wide circular openings in the nuclear envelope. An NPC can open to 25 nm in diameter. For passage across, proteins do not need to be kept in an unfolded configuration. Unlike protein conducting channels, NPCs are unable to integrate proteins into the lipid bilayer. Furthermore, transport across the NPC is bidirectional. Also, transport is not limited to proteins but includes ribonucleoproteins (RNPs). An in vitro system for signal sequence-mediated protein uptake into the nucleus has been used to isolate and to characterize cytosolic factors that are required for import. Similar in vitro RNP export systems are being developed to study export of RNPs. NPCs have been purified in quantity from yeast. An estimated 100 or so proteins make up the NPC. The challenge ahead here is to understand the structure and function of these NPC proteins and of NPC as a whole.
John D. Rockefeller, Jr. Professor; Investigator, HHMI
The unidirectional translocation of thousands of distinct proteins across specific intracellular membranes is mediated by "signal" sequences. On average, a signal sequence consists of a stretch of ~15 amino acid residues that is either a transient or permanent part of the protein to be translocated. The signal sequence functions essentially as a ligand. Each signal sequence is membrane specific and is decoded by a complex machinery that is restricted in its location to one particular cellular membrane.
Two distinct mechanisms of translocation have so far been discovered. In one mechanism translocation proceeds through protein conducting channels. The diameter of the aqueous center of these protein conducting channels is limited (~2 nm) so that passage of a protein can proceed only in its unfolded configuration. A number of polypeptide binding proteins assist in keeping the protein to be translocated in an unfolded configuration. Protein conducting channels have recently been detected electrosphysiologically in the endoplasmic reticulum and the prokaryotic plasma membrane. These channels were found to be gated open by the signal sequence. The channel closes after translocation of the chain is completed. In addition to opening and closing across the membrane, the channel must also be able to open and close in a second dimension, namely to the lipid bilayer. This is necessary to permit integration of proteins into membranes. A protein to be integrated into the membrane uses a signal sequence to open the channel. Translocation proceeds until a "stop transfer" sequence of the translocating polypeptide chain interacts with the channel to open it laterally to the lipid bilayer. As a result, the segment of the chain that is located in the channel would be displaced into the bilayer with the channel simultaneously closing in both dimensions. Similar protein conducting channels are likely to exist in the outer as well as the inner membrane of chloroplasts and mitochondria, in the thylakoid membrane of chloroplasts, and in the peroxisomal membrane. The great challenge ahead is to isolate and to characterize these protein conducting channels.
The mechanism of protein translocation across the nuclear pore complex (NPC) is distinct from that of translocation across the above-described protein conducting channels. NPCs are huge organelles (estimated molecular mass: 125 million daltons) that are suspended in 100-nm wide circular openings in the nuclear envelope. An NPC can open to 25 nm in diameter. For passage across, proteins do not need to be kept in an unfolded configuration. Unlike protein conducting channels, NPCs are unable to integrate proteins into the lipid bilayer. Furthermore, transport across the NPC is bidirectional. Also, transport is not limited to proteins but includes ribonucleoproteins (RNPs). An in vitro system for signal sequence-mediated protein uptake into the nucleus has been used to isolate and to characterize cytosolic factors that are required for import. Similar in vitro RNP export systems are being developed to study export of RNPs. NPCs have been purified in quantity from yeast. An estimated 100 or so proteins make up the NPC. The challenge ahead here is to understand the structure and function of these NPC proteins and of NPC as a whole.
Pietro De Camilli
Pietro De Camilli is an Italian-American biologist and Eugene Higgins Professor of Cell Biology at Yale University School of Medicine. He is also an Investigator at Howard Hughes Medical Institute.
De Camilli completed his M.D. degree from the University of Milan in Italy. He then went to the United States and did his postdoctoral studies at Yale University.
De Camilli is known for contributions that has been to demonstrate the crucial role of protein-lipid interactions and phosphoinositide metabolism in the control of membrane traffic at the synapse.
He has received several awards and honors for his work. He was elected to the European Molecular Biology Organization in 1987. In 2001, he was elected to the National Academy of Sciences and to the American Academy of Arts and Sciences. In 1990 he received the Max-Planck-Forschungspreis together with Reinhard Jahn (Max Planck Institute of Psychiatry).
During synaptic transmission, neurotransmitter-containing vesicles fuse with the plasma membrane, releasing neurotransmitters into the synaptic space by exocytosis. In the subsequent seconds, vesicle membranes are reinternalized and reused for the next generation of synaptic vesicles. Over the last 25 years, Pietro De Camilli has studied the molecular mechanisms involved in this intricate cycle of membrane traffic and has identified and characterized numerous proteins that participate in the process. Trained as an M.D., he has also made significant contributions toward understanding human diseases of the nervous system that involve autoimmunity against synaptic proteins. Because the synaptic vesicle is a powerful model organelle for studying fundamental mechanisms in membrane-cytoskeletal interactions, membrane fusion, and membrane budding, De Camilli's discoveries are relevant to secretory and endocytic mechanisms in many fields beyond neurotransmission.
De Camilli completed his M.D. degree from the University of Milan in Italy. He then went to the United States and did his postdoctoral studies at Yale University.
De Camilli is known for contributions that has been to demonstrate the crucial role of protein-lipid interactions and phosphoinositide metabolism in the control of membrane traffic at the synapse.
He has received several awards and honors for his work. He was elected to the European Molecular Biology Organization in 1987. In 2001, he was elected to the National Academy of Sciences and to the American Academy of Arts and Sciences. In 1990 he received the Max-Planck-Forschungspreis together with Reinhard Jahn (Max Planck Institute of Psychiatry).
During synaptic transmission, neurotransmitter-containing vesicles fuse with the plasma membrane, releasing neurotransmitters into the synaptic space by exocytosis. In the subsequent seconds, vesicle membranes are reinternalized and reused for the next generation of synaptic vesicles. Over the last 25 years, Pietro De Camilli has studied the molecular mechanisms involved in this intricate cycle of membrane traffic and has identified and characterized numerous proteins that participate in the process. Trained as an M.D., he has also made significant contributions toward understanding human diseases of the nervous system that involve autoimmunity against synaptic proteins. Because the synaptic vesicle is a powerful model organelle for studying fundamental mechanisms in membrane-cytoskeletal interactions, membrane fusion, and membrane budding, De Camilli's discoveries are relevant to secretory and endocytic mechanisms in many fields beyond neurotransmission.
Prominent researchers- HHMI
Michael D Ehlers.
http://www.ehlerslab.org/
Michael D. Ehlers, M.D., Ph.D. (Young Investigator 2000) of Duke University Medical Center, aims to determine the molecular mechanisms which regulate the localization and function of NMDA receptors. These receptors play important roles in learning and memory, brain development, and neuropsychiatric disease. Dr. Ehlers will identify new regulatory molecules associated with NMDA receptors, determine the effect of phosphorylation (addition of a phosphate molecule) on these receptors, and determine which domains of the NMDA receptor localize it to synapses (the spaces between adjacent neurons). These studies may provide a crucial step in understanding the function of the NMDA receptors, which may facilitate the design of rational strategies for the treatment of neurologic and psychiatric disease, such as schizophrenia.
http://www.ehlerslab.org/
Michael D. Ehlers, M.D., Ph.D. (Young Investigator 2000) of Duke University Medical Center, aims to determine the molecular mechanisms which regulate the localization and function of NMDA receptors. These receptors play important roles in learning and memory, brain development, and neuropsychiatric disease. Dr. Ehlers will identify new regulatory molecules associated with NMDA receptors, determine the effect of phosphorylation (addition of a phosphate molecule) on these receptors, and determine which domains of the NMDA receptor localize it to synapses (the spaces between adjacent neurons). These studies may provide a crucial step in understanding the function of the NMDA receptors, which may facilitate the design of rational strategies for the treatment of neurologic and psychiatric disease, such as schizophrenia.
Friday, January 9, 2009
Sunday, November 16, 2008
Saturday, November 8, 2008
the structure of striatum
http://www.ploscompbiol.org/article/info:doi%2F10.1371%2Fjournal.pcbi.0020176
Introduction
The basal ganglia of mammals are made up of several nuclei forming large processing circuits in the forebrain and controlled by mesencephalic dopamine (DA) neurons [1]. The dorsal nigrostriatal DA pathway modulates the cortico–striato–thalamic loop [2] involved in extrapyramidal motor and cognitive functions. The ventral mesolimbic DA pathway supports a variety of behavioural functions related to motivation and reward [3]. The functional diversity of the basal ganglia is mirrored by their involvement in pathological conditions as diverse as Parkinson disease, Huntington chorea, schizophrenic syndromes, and drug addiction. The main inputs of the striatum are the excitatory glutamatergic projections from pyramidal neurons of the cortex [4,5]. The GABAergic medium-sized spiny neurons, which comprise more than 95% of the striatal neurons, give rise to two kinds of projections. A direct “stimulatory” pathway projects to the output structures, internal globus pallidus, and substantia nigra pars reticulata, while an indirect, “depressant” pathway projects to the same nuclei via the external globus pallidus and the subthalamic nucleus [6]. The indirect pathway forms an incoherent feedforward loop (that is in the same direction as the direct pathway but with opposite effect), that modulates the effect of the direct pathway. The balance between those two pathways is crucial for the function of basal ganglia. DA released in striatum potentiates the function of the direct pathway, through D1 receptors, and acts as a psychostimulant (enhancing locomotion and elevating mood). In addition, DA inhibits the function of the indirect pathway through D2 receptors. The disappearance of this control contributes to the clinical symptoms of Parkinson disease.
Introduction
The basal ganglia of mammals are made up of several nuclei forming large processing circuits in the forebrain and controlled by mesencephalic dopamine (DA) neurons [1]. The dorsal nigrostriatal DA pathway modulates the cortico–striato–thalamic loop [2] involved in extrapyramidal motor and cognitive functions. The ventral mesolimbic DA pathway supports a variety of behavioural functions related to motivation and reward [3]. The functional diversity of the basal ganglia is mirrored by their involvement in pathological conditions as diverse as Parkinson disease, Huntington chorea, schizophrenic syndromes, and drug addiction. The main inputs of the striatum are the excitatory glutamatergic projections from pyramidal neurons of the cortex [4,5]. The GABAergic medium-sized spiny neurons, which comprise more than 95% of the striatal neurons, give rise to two kinds of projections. A direct “stimulatory” pathway projects to the output structures, internal globus pallidus, and substantia nigra pars reticulata, while an indirect, “depressant” pathway projects to the same nuclei via the external globus pallidus and the subthalamic nucleus [6]. The indirect pathway forms an incoherent feedforward loop (that is in the same direction as the direct pathway but with opposite effect), that modulates the effect of the direct pathway. The balance between those two pathways is crucial for the function of basal ganglia. DA released in striatum potentiates the function of the direct pathway, through D1 receptors, and acts as a psychostimulant (enhancing locomotion and elevating mood). In addition, DA inhibits the function of the indirect pathway through D2 receptors. The disappearance of this control contributes to the clinical symptoms of Parkinson disease.
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