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Lab presentation

Our group is interested in unveiling the molecular mechanisms supporting endocytic traffic, with a particular focus in the characterization of actin scaffolds that transiently assemble at the plasma or endosomal membranesto aid budding and fission. We investigate the components of these endocytic actin scaffolds, the physico-chemical parameters that regulate their assembly and turn over, and theirparticular architecture and coupling to membranes, which ultimately drive membrane deformation with a defined geometry.

To this end, we mostly use S. cerevisiae as a model system, but we also extend our investigations to mammalian cells. By combining the powerful yeast genetics or the crispr cas9 technology in mammalian cells, together with actin polymerization in vitro assays, live-cell fluorescence imaging of single endocytic events and sophisticated time-resolved ultrastructural analysis, we provide data to refine molecular models explaining membrane deformation, and we uncover mechanisms regulating actin nucleating promoting factors such as type I myosins, N-WASP,cortactin or WASH.

Our research has led to the discovery of new functions or regulators of conserved proteins whose mutation in humans causeinherited renal, immunological and neurological diseases such as focal segmental glomerulosclerosis (myo IE, ORPHA93213), theWiskott–Aldrich syndrome (N-WASP, ORPHA906), amyotrophic lateral sclerosis (VAPs, ORPs, ORPHA209335), atypical juvenile parkinsonism (SNJ1, ORPHA:391411) or autosomal dominant non-syndromic intellectual disability (CKB1, ORPHA:178469).This information is key to understand their role in health and disease and has identified potential therapeutic targets to ameliorate the symptoms of individuals that bear mutations in these genes.

Projects

Research Lines:

  • To define the basic molecular mechanisms supporting endocytic traffic:
    Protein and membrane traffic through out the endocytic pathway requires a core machinery effecting membrane budding, vesicle and organelle motility and membrane fusion, which is conserved from yeast to humans. We aim to identify the minimal set of evolutionary-conserved proteins required to support some of these events (with a particular focus in membrane budding), to understand the mechanical forces involved and to define the molecular signals that target cargo into endocytic transport intermediates.
  • To identify the molecular machinery that adapts the endocytic traffic:
    To identify the molecular machinery that adapts the endocytic traffic in higher eukaryotes to fulfil specialized physiological functions such as the regeneration of synaptic vesicles in neurons, the control of cell adhesion, the presentation of antigens by the immune system or the establishment of morphogen gradients during development. We aim to identify proteins, accessory to the endocytic core machinery, that play a role in those processes. Such accessory proteins might be the target of therapeutical strategies destined to alleviate human diseases where endocytosis plays an important role, such as cancer or neurodegeneration.

Projects:

1. Function and regulation of ER-endocytic contact sites and the mechanism of sterol-induced actin polymerization.
We previously demonstrated that the endoplasmic reticulum (ER) contacts the endocytic sites to facilitate actin polymerization and membrane invagination during endocytic uptake. We found that the molecular link between the cER and the endocytic sites is composed of the yeast homologs of the human VAP (VAMP Associated Proteins) A and B, Oxysterol binding protein Related Proteins (ORPs) and the endocytic type I myosins (Encinar del Dedo et al Dev. Cell (2017)). Our data indicate that the VAP/ORP/Myosin-I complex has the capacity to transfer sterols to the plasma membrane, and that this activity is specifically required to concentrate and activate the type I myosins,which in turn initiate actin polymerization at endocytic sites. We are now in the process of characterizing the molecular link between the sterols and the recruitment and activation of actin nucleator promoting factors, which might involve the activation of a PI4P-5 kinase, calcium channels, small GTPases and/or the formation of lipid rafts. On the other hand, we have recently found that thecER rims that contact the endocytic sites are specialized subdomains where sterol synthesis and ORP-dependent extraction are physically coupled. Hence, we have named these subdomains as ER Sterol Synthesis and Exit Sites (ERSSES). We are currently characterizing the components of the ERSSES and defining its function and regulation.

2. Transient assembly of macromomolecular complexes; regulation by phosphoinositides and CK2.
We previously found that the yeast synaptojanins,which hydrolyze the 4 and 5 phosphates of PIns(4,5)P2, cooperate with the promiscuous casein kinase 2 (CK2) to disassemble the actin scaffold induced by N-WASP and type I myosins at endocytic sites (Fernández-Golbano (2014) Dev Cell). Disassembly occurs in a very narrow time window,indicating that a mechanism coordinating the synaptojanin and CK2 activities might exist. Interestingly, we found that PIns(4,5)P2 binds and inhibits CK2 in vitro, so that its activity towards endocytic proteins might only be triggered upon hydrolysis of PIns(4,5)P2 by the synaptojanins. What is the physiological relevance of this mechanism in vivo remained to be demonstrated. At the moment, we are conducting structural biology experiments to define the PIns(4,5)P2 binding site in CK2and understand the mechanism of CK2 inhibition by the phosphoinositides. Identification of the PIns(4,5)P2 binding site will allow us to investigate the physiological meaning of the phosphoinositide/CK2 crosstalkin many contexts.On the other hand, since CK2 binds several phosphoinositides, we hypothesized that CK2 might control the disassembly of other macromolecular complexes that transently assembly in respond tophosphoinositides. A phosphoproteomic approach indeed identified some of these modules, which are enriched in proteins bearing intrinsically disordered domains (IDRs). We are now testing the hypothesis that CK2 cooperate to trigger the fast disassembly of thosecomplexes by targeting theirIDRs.

3. A multivalent regulator of endosomal traffic in mammalian cells that regulates actin polymerization and tubulin-dependent transport.
We identified kazrin C as a human protein that inhibits clathrin-mediated endocytosis when overexpressed. We have generated kazrin knock out and GFP-kazrin C knock in mouse embryonic fibroblast to investigate its function in endocytic trafficking.We found that kazrin depletion causes a defect in traffic from early (EE) to recycling endosomes (RE). Cellular functions that require unaltered endocytic recycling, such as cell migration or cytokinetic abscission, are also affected in the knock out cells. Consistent with its function, endogenous kazrin is detected on EE and interacts with several components of these organelles, including Epsin Homology Domain proteins EHD1 and EHD3, gamma adaptinand phosphatidyl-inositol-3 phosphate. In vivo, we found that overexpression of GFP-kazrin Cforms a condensate that entraps EE in the vicinity of the centromere, suggesting that kazrin is either an endosomal adaptor for dynein or it retains dynein cargo in the pericentriolar region.Further, we found that kazrin inhibits actin polymerization on EE membranes.The data thus suggest that kazrin is a multivalent regulator of endocytic recycling that promotes microtubule dependent traffic or retention of EE at the perinuclear region, while it downregulatesendosomal actin polymerization. We are currently conducting experiments to define the actin nucleating promoting factors directly regulated by kazrin, and define its possible interaction with dynein and the dynactin complex.

Lab people

Principal investigator

After her Ph. D. in plant cell biology, M. I. Geli moved to the laboratory of H. Riezman at the Biozentrum of the University of Basel, where she contributed to identify several proteins involved in endocytosis, including the unconventional type I myosins (Geli and Riezman 1996 Science). In January 1999, M. I. Geli started her scientific career as an independent researcher at the Biochemie-Zentrum of the University of Heidelberg, where she established a research line to understand how the transient assembly of macromolecular complexes can drive deformation of cellular membranes. In 2003, she got a tenior position as Científico Titular of the CSIC at the Instituto de Biología Molecular de Barcelona where she was promoted to Investigador Científico in 2009.

Since 2014, she is Deputy Director of the IBMB, and since 2020 she is member of the Editorial Boards of eLife and Current Research in Cell Biology. Along her carrier as principal investigator, M. I. Geli has made significant contributions to the field, which include the description of the molecular mechanisms underlying the regulation of type I myosins (Geli et al 1998 EMBO J, and Grötsch et al 2010 EMBO J); the development of time-resolved electron microscopy to study endocytic budding with unprecedented resolution (Idrissi et al 2008 J Cell Biol and Idrissi et al 2010 PNAS), the description a phosphoinositide/CK2 interplay (Fernandez-Golbano et al 2014 Dev. Cell.) and the discovery and functional characterization of the ER endocytic contact sites (Encinar del Dedo et al., in revision for Dev. Cell).

Past students

Adrian Baumann

PhD Student

Selected publications

M. I. Geli and H. Riezman (1996) “Role of type I myosins in receptor-mediated endocytosis in yeast” Science 272, 533-5.


M. I. Geli, A. Wesp and H. Riezman (1998) “Distinct functions of calmodulin are required for the uptake step of receptor mediated-endocytosis in yeast: the type I myosin Myo5p is one of the calmodulin targets” EMBO J. 17, 635-47.


M. I. Geli*, B. Schmelzl, R. Lombardi, and H. Riezman (2000) “An intact SH3 domain is required for myosin-I induced actin polymerization” EMBO J. 19, 4281-91.


B. Schmelzl, and M. I Geli (2002) “An efficient genetic screen in mammalian cultured cells” EMBO Rep. 3, 683-87.


F.-Z. Idrissi, H. Grötsch, I. M. Fernández-Golbano, C. Presciatto-Baschong, H. Riezman and M. I. Geli (2008) “ Distinct acto/myosin-I structures associate with endocytic profiles at the plasma membrane” J. Cell Biol. 180: 1219-32.


H. Grötsch, J. P. Giblin, F. Z. Idrissi, I. M. Fernández-Golbano, J. R. Collette, T. M. Newpher, V. Robles, S. K. Lemmon, M. I. Geli “Calmodulin dissociation regulates Myo5 recruitment and function at endocytic sites” EMBO J. (2010) 29: 2899-914.


F-Z.Idrissi, A. Blasco, A. Espinal and M. I.Geli.“Ultrastructural dynamics of proteins involved in endocytic budding” (2012) ProcNatlAcadSci U S A. 109: E2587-94.


A. Herms, M. Bosch, N. Ariotti, B. J. Reddy, A. Fajardo, A. Fernández-Vidal, A. Alvarez-Guaita, M. A. Fernández-Rojo, C. Rentero, F. Tebar, C. Enrich, M. I.Geli, R. G. Parton, S. P. Gross and A.Pol. (2013) “Cell-to-Cell Heterogeneity in Lipid Droplets Suggests a Mechanism to Reduce Lipotoxicity”Curr Biol. 23:1489-96.


I-M. Fernández-Golbano, F-Z. Idrissi, J. P. Giblin, B. L. Grosshans, V. Robles, H. Grötsch, M.M. Borrás and M- I. Geli*. “A cross-talk between PI(4,5)P2 and CK2 modulates actin polymerization during endocytic uptake” (2014) Dev Cell. 30, 746-758.


Amaral N, Vendrell A, Funaya C, Idrissi FZ, Maier M, Kumar A, Neurohr G, Colomina N, Torres-Rosell J, Geli MI, Mendoza M. (2016) The Aurora-B-dependent NoCut checkpoint Prevents damage of anaphase bridges after DNA replication stress.NatCell Biol. 18:516-26.


J. Encinar del Dedo, F-Z. Idrissi, P. Garcia, I. M. Fernandez-Golbano1, E. R., M. K. Krzyzanowski, H. Grötsch, M. I. Geli. “ORP-Mediated ER Contact with Endocytic Sites Facilitates Actin Polymerization”(2017) Dev Cell. 43, 588-602.


J.Encinar del Dedo, I-M. Fernández-Golbano, P. Meler, E. Rebollo, M. I. Geli. “Endoplasmic Reticulum Sterol Synthesis and Exit Sites” (2020) Sci. Adv.Under revision.

All publications

Research Articles and Reviews (First or corresponding Authorship)


M. I. Geli, M. Torrent and D. Ludevid (1994) “Two structural domains mediate two sequential events in -Zein targeting: protein endoplasmic reticulum retention and protein body formation”Plant Cell 6, 1911-22.


M. I. Geli and H. Riezman (1996) “Role of type I myosins in receptor-mediated endocytosis in yeast” Science 272, 533-5.


M. I. Geli, A. Wesp and H. Riezman (1998) “Distinct functions of calmodulin are required for the uptake step of receptor mediated-endocytosis in yeast: the type I myosin Myo5p is one of the calmodulin targets” EMBO J. 17, 635-47.


M. I. Geli and H. Riezman (1998) “Endocytic internalization in yeast and animal cells: similar and different” J. Cell Sci. 111, 1031-37.


M. I. Geli*, B. Schmelzl, R. Lombardi, and H. Riezman (2000) “An intact SH3 domain is required for myosin-I induced actin polymerization” EMBO J. 19, 4281-91. * Corresponding author
B. Schmelzl, and M. I Geli (2002) “An efficient genetic screen in mammalian cultured cells” EMBO Rep. 3, 683-87.


F.Z. Idrissi, B.L. Wolf, and M.I. Geli (2002) “Cofilin, but not profilin, is required for Myosin-I-induced actin polymerization and the endocytic uptake in yeast” Mol. Biol. Cell.13, 4074-87.


B. L.Großhans, H. Grötsch, D. Mukhopadhyay+, I. M. Fernández, J. Pannsfield, F.-Z. Idrissi, J. Lechner, H. Riezmanand M. I. Geli (2006) “TEDS site phosphorylation of the yeast myosins-I is required for ligand-induced but not for constitutive endocytosis of the G protein-coupled receptor Ste2p”. J. Biol. Chem.281, 11104-14.


F.-Z. Idrissi, H. Grötsch, I. M. Fernández-Golbano, C. Presciatto-Baschong, H. Riezman and M. I. Geli (2008) “ Distinct acto/myosin-I structures associate with endocytic profiles at the plasma membrane” J. Cell Biol. 180: 1219-32.


F-Z.Idrissi, M. I. Geli* and H. Girao (2008) “Actin in the endocytic pathway: from yeast to mammals” FEBS Letters.(2008) 582: 2112-9.* Corresponding author
H. Grötsch, J. P. Giblin, F. Z. Idrissi, I. M. Fernández-Golbano, J. R. Collette, T. M. Newpher, V. Robles, S. K. Lemmon, M. I. Geli “Calmodulin dissociation regulates Myo5 recruitment and function at endocytic sites” EMBO J. (2010) 29: 2899-914.


J. Giblin, I. M. Fernández-Golbano, F. Z. Idrissi, M. I.Geli “Function and regulation of Saccharomyces cerevisiaemyosins-I in endocytic budding.”Biochem.Soc. Trans.(2011)39:1185-90.


F-Z.Idrissi, A. Blasco, A. Espinal and M. I.Geli.“Ultrastructural dynamics of proteins involved in endocytic budding” (2012) ProcNatlAcadSci U S A. 109: E2587-94.


F-Z.Idrissi and M. I.Geli. “Zooming in on the molecular mechanisms of endocytic budding by time-resolved electron microscopy” (2014) Cell Mol Life Sci.71(4):641-57
I-M. Fernández-Golbano, F-Z. Idrissi, J. P. Giblin, B. L. Grosshans, V. Robles, H. Grötsch, M.M. Borrás and M- I. Geli*. “A cross-talk between PI(4,5)P2 and CK2 modulates actin polymerization during endocytic uptake” (2014) Dev Cell. 30, 746-758.


J. Encinar del Dedo, F-Z. Idrissi, P. Garcia, I. M. Fernandez-Golbano1, E. R., M. K. Krzyzanowski, H. Grötsch, M. I. Geli. “ORP-Mediated ER Contact with Endocytic Sites Facilitates Actin Polymerization”(2017) Dev Cell. 43, 588-602.


J.Encinar del Dedo, I-M. Fernández-Golbano, P. Meler, E. Rebollo, M. I. Geli. “Endoplasmic Reticulum Sterol Synthesis and Exit Sites” (2020) Sci. Adv.Under revision.


 

Other Research Articles and Reviews


M. Torrent, M. I. Geli and D. Ludevid (1989) “Storage-protein hydrolysis and protein body breakdown in germinated Zea mays L. seeds” Planta 180, 90-5.


M. Torrent, M. I. Geli, L. Ruiz-Avila, J.M.Canals, P. Puigdomènech and D. Ludevid. (1994) “Role of structural domains for maize -Zein retention in Xenopus oocytes”. Planta 192, 512-18.


A. L. Munn, B. J. Stevenson, M. I. Geli and H. Riezman (1995) “end5, end6 and end7: mutations that cause actin delocalization and block the internalization step of endocytosis in Saccharomyces cerevisiae.” Mol. Biol. Cell. 6, 1721-42.


H. Riezman, A. Munn, M. I. Geli and L. Hicke (1996) “Actin- myosin- and ubiquitin-dependent endocytosis”. Experientia52, 1033-41. (Review).


M. Torrent, I. Alvarez, M. I. Geli, I. Dalcol and D. Ludevid (1997) “Lysine-rich modified -Zein accumulates in protein bodies of transiently transformed maize endosperms”. Plant Mol. Biol. 34, 139-49.


I. Alvarez, M. I. Geli, E. Pimentel, D. Ludevid and M. Torrent. (1998) “Lys-rich -Zeins are secreted in transgenic Arabidopsis plants”.Planta.205, 420-27.


J.S. Chang, K. Henry, B.L. Wolf, M. I. Geli, and S.K. Lemmon (2002) “Protein phosphatase-1 binding to scd5p is important for regulation of actin organization and endocytosis in yeast” J. Biol. Chem. 277:48002-8.


J. S. Chang, K. Henry, M. I. Geli and S. K. Lemmon(2006) “Cortical Recruitment and Nuclear-Cytoplasmic Shuttling of Scd5p, a Protein Phosphatase- 1 Targeting Protein Involved in Actin Organization and Endocytosis”. Mol. Biol. Cell. 17:251-62.


T. Newpher, F. Z. Idrissi, M. I. Geli and S. K. Lemmon (2006) “Novel Function of Clathrin Light Chain in Promoting Endocytic Vesicle Formation” Mol. Biol. Cell.17:4343-52.


G. P. Singh, G. Volpe, C. M. Creely, H. Grötsch, M. I.Geli and D. Petrov(2006) ”The lag phase and G1 phase of a single yeast cell monitored by Raman microspectroscopy” J. of Raman Spec.37, 858-864.


A. C. De Luca, G. Volpe, A. Morales Drets, M. I. Geli, G. Pesce, G. Rusciano, A. Sasso, D. Petrov (2007). Real-time actin-cytoskeleton depolymerization detectionin a single cell using optical tweezers. Optic Express.(2007) 15, 7922-7932.


J. R. Collette, R. J. Chi, D. R. Boettner, I. M. Fernandez-Golbano, R. Plemel, A. J. Merz, M. I. Geli, L. M. Traub and S. K. Lemmon. Clathrin Functions in the Absence of the Terminal Domain Binding Site for Adaptor-associated Clathrin-Box Motifs.(2009) MolBiol Cell.20, 3401-3413.


A. Herms, M. Bosch, N. Ariotti, B. J. Reddy, A. Fajardo, A. Fernández-Vidal, A. Alvarez-Guaita, M. A. Fernández-Rojo, C. Rentero, F. Tebar, C. Enrich, M. I.Geli, R. G. Parton, S. P. Gross and A.Pol. (2013) “Cell-to-Cell Heterogeneity in Lipid Droplets Suggests a Mechanism to Reduce Lipotoxicity”Curr Biol. 23:1489-96.


Encinar del Dedo J, Idrissi FZ, Arnáiz-Pita Y, James M, Dueñas-Santero E, Orellana-Muñoz S, del Rey F, Sirotkin V, Geli MI, Vázquez de Aldana CR. (2014) Traffic. 15:1122-42.


Amaral N, Vendrell A, Funaya C, Idrissi FZ, Maier M, Kumar A, Neurohr G, Colomina N, Torres-Rosell J, Geli MI, Mendoza M. (2016) The Aurora-B-dependent NoCut checkpoint Prevents damage of anaphase bridges after DNA replication stress.NatCell Biol. 18:516-26.


Pons M, Izquierdo I, Andreu-Carbó M, Garrido G, Planagumà J, Muriel O, Geli MI, Aragay AM. Regulation of chemokine receptor CCR2 recycling by filamin a phosphorylation.J. Cell Sci. 2016. 15:490-501.


Project funding

Research Grants awarded to M.I.G.

1999-2003
SFB 352, Molecular Mechanisms of the Intracellular Transport Processes
Granted by the DeustcheForschungsgemeinschaft


2000
SPP 1068, Molecular Motors
Granted by the theDeustcheForschungsgemeinschaft


2002-2004
Grauiertkolleg of the University of HeidelbergPh. D. fellowship


2003-2005
SAF2002-04707: Estudio de la endocitosis asociada a rafts lipídicos
GrantedbytheMinisterio de Ciencia y Tecnología
FPI predoctoral fellowship from the Spanish Government (2003 to 2006)
FI predoctoralfellowship from the Catalan Government (2004 to 2007)


2006-2008
BFU2005-04089: Estudio de la endocitosis asociada a rafts lipídicos
GrantedbytheMinisterio de Educación y Ciencia
Postdoctoral fellowship from the Portuguese Government (2006-2007)
Postdoctoral fellowship from the Spanish Government (2006-2010)


2009-2011
BFU2008-03500: Actin-dependent endocytosis
GrantedbytheMinisterio de Educación y Ciencia
FPI predoctoral fellowship (2009-2012)
Technician fellowship from the CSIC (2009-2011)
Postdoctoral fellowship from the CSIC (2009-2011)


2009-2012
2009SGR41635: Mechanism and function of endocytic traffic
Granted by the Generalitat de Catalunya


2010-2014
CSD2009-00016: Mechanism of Protein Secretion and Compartment Organization.
GrantedbytheMinisterio de Ciencia y Tecnología


2011-2014
BFU2011-30185:Mechanism and physiologicalfunctions of endocytosis
GrantedbytheMinisterio de Ciencia y Tecnología
FPI predoctoral fellowship (2012-2015)


2015-2017
BFU2014-59765-P: Mechanism and physiological functions of endocytosis
GrantedbytheMinisterio de Ciencia y Tecnología
FPI predoctoralfellowship (2015-2018)
Postdoctoral contract Juan de la Cierva (2015-2016)


2017-2019
BFU2016-81912-REDC: Organización compartimental y transporte
GrantedbyMinisterio de Ciencia, Innovación y Universidades


2018-2020
BFU2017-82959P: Molecular mechanisms of endocytosis
GrantedbyMinisterio de Ciencia, Innovación y Universidades
FPI predoctoral fellowship from the Spanish government

Vacancies/Jobs

If you are interested in joining the lab as postdoc or PhD student please send us your CV and cover letter: Maribel Geli (mgfbmc@ibmb.csic.es).

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