Roberto Sitia
Roberto Sitia
affiliation: Università Vita-Salute San Raffaele
research area(s): Cell Biology, Molecular Biology
  • Cell and Molecular Biology
  • Basic and Applied Immunology
University/Istitution: Università Vita-Salute San Raffaele
University of Genoa, Italy MD 1977 Medicine (cum laude)
University of Genoa, Italy Specialist 1980 Hematology (cum laude)
Memorial Sloan Kettering Cancer Center Post Doc 1979 Immunochemistry

1978-1979 Post Doctorate Fellow, Immunochemistry, Memorial Sloan Kettering Cancer Center, New York
1980-1982 Assistant Professor, Immunology and Transplantation, University of Genoa, Italy
1982-1986 Assistant Professor, Molecular Biology, National Cancer Center, Genoa Italy
1986-1987 Visiting Investigator, Laboratory of Molecular Biology, Cambridge, UK
1987-1990 Associate Professor, Immunogenetics, National Cancer Center, Genoa Italy
1990- Group leader, San Raffaele Scientific Institute, Milano
1998-2007 Deputy Director, Department of Functional Genomics and Molecular Biology,
San Raffaele Scientific Institute, Milano
2000- Professor of Molecular Biology, Università Vita Salute San Raffaele. Milano
2005-2007 Dean of the School of Medicine, Università Vita Salute San Raffaele. Milano
2008- Director, Division of Genetics and Cell Biology, San Raffaele Scientific Institute, Milano
Roberto Sitia, MD, is Professor of Molecular biology at University Vita-Salute San Rafaele, and Director of the Division of Genetics and Cell Biology at SRSI.
His scientific interests have been centered on the mechanisms that regulate antibody production. Having started with an immunochemical approach, he characterized in the early 80s a B Cell lymphoma inducible to isotype switching and Ig secretion. In the late 80s, during a sabbatical period in César Milstein's laboratory in Cambridge, he was amongst the firsts to fuse immunology and cell biology: his work contributed significantly to our current understanding of the 'quality control' of secretory proteins. Of remarkable importance are the discoveries of thiol-mediated retention, one of the main mechanisms of endoplasmic reticulum (ER) quality control, of the 'leaderless' secretory pathway, utilised by proteins like bFGF and IL1" that lack a signal peptide, and the characterization of the biogenesis of Russell Bodies in myeloma cells, a robust model of ER storage disorders (Valetti et al., J Cell Biol, 1991; Ronzoni et al., Traffic, 2010). His laboratory has cloned and characterized many human genes involved in the regulation of ER stress responses and redox homeostasis (Anelli et al., EMBO J, 2002, 2003, 2007, 2008; Rubartelli & Sitia, ARS and Nature Chem Biol, 2009; Margittai & Sitia, ARS, 2011), characterized the proteins that are expressed during terminal B cell differentiation (van Anken et al., Immunity, 2003; Bertolotti et al., 2010, ARS), and demonstrated that an unfavourable proteasome load versus capacity ration explains the differential sensitivity of normal and malignant plasma cells to proteasome inhibitors, a class of drugs very active against multiple myeloma (Cenci et al., EMBO J, 2006; Bianchi et al., Blood, 2009; Cenci et al. Curr Op. Cell Biol 2011)
Member of the European Molecular Biology Organisation (EMBO) since 1992, RS has chaired the EMBO Science and Society Committee and was a Co-founder and member of the Organising Committee of the European Life Sciences Organisation. He is an Editor of The EMBO Journal, EMBO reports and Antioxidant Redox Signaling.
His Laboratory (Protein Transport and Secretion) focuses on the biogenesis, folding and quality control of proteins destined to the extracellular space. Particular emphasis is given to the mechanisms controlling disulfide bond formation and redox regulation, and their relevance in proteostasis and signalling.
The lab is now analysing the structure, function and regulation of Ero1α a master ER oxidase (Inaba et al, EMBO J, 2010; Masui et al., JBC, 2011) and ERp44, a multifunctional chaperone of the early secretory compartment (Wang et al., EMBO Rep 2008; Fraldi et al. Hum Mol Gen, 2008).
The terminal differentiation of B lymphocytes into plasma cells provides a most powerful model to unravel the organellar reshaping and dynamic proteostasis rearrangements underlying differentiation and lifespan control (van Anken et al., Immunity, 2003; Cenci & Sitia, FEBS, 2007; Venè et al. ARS, 2010).
The lab occupies a leading position in the control and pathophysiology of IgM folding, polymerization and secretion (Anelli & Sitia, Sem Cell Biol 2010; Cortini & Sitia, Traffic, 201o)
Many of the basic findings are rapidly translating into the clinics. For instance, the downregulation of proteasomes during plasma cell differentiation explains the exquisite sensitivity of normal and malignant plasmacells to Bortezomib and other drugs affecting proteostasis (Cenci et al. Curr Op Cell Biol., 2011).

The lab has two tenured technicians, one responsible for molecular biology and biochemistry and the other on animal care and tissue culture, guarantee continuity in reagents and techniques. There are generally 3 postDocs, 2-3 PhD students and several undergraduate and Master students preparing their theses.
Joint lab meetings are held weekly with Eelco van Anken"s and Simone Cenci"s groups (ER signalling and Biology of aging)

Collaborations are ongoing with Drs. Kaz Nagata (Kyoto, JP, functional role of peroxiredoxin 4); Kenji Inaba (Fukuoka, JP, the structure and function of ERp44 and Ero1a); Anna Rubartelli (Genoa, IT, the redox regulation of B cell differentiation); G.Banhegi and M.Geistz (Budapest HU) and Seva Belousov (Moscow, RU) for the development of hydrogen peroxide sensors
Cenci S, Van Anken E and Sitia R. (2011) Proteostenosis and plasma cell pathophysiology. Curr. Opin. Cell Biol. 23, 216-222

Margittai E and Sitia R. (2011). Oxidative protein folding in the secretory pathway and redox-signaling across compartments and cells. Traffic, 12, 1-8.

Masui S, Vavassori S, Fagioli C, Sitia R, Inaba K. (2011) Molecular bases of cyclic and specific disulfide interchange between human Ero1{alpha} and PDI. J Biol Chem. Mar 11. [Epub ahead of print]

Bertolotti M, Yim SH, Garcia-Manteiga JM, Masciarelli S, Kim YJ, Kang MH, Iuchi Y, Fuji J, Venè R, Rubartelli I A, Rhee SG, Sitia R. (2010). B- to plasma-cell terminal differentiation entails oxidative stress and profound reshaping of the antioxidant responses. Antioxid. Redox Signal., 13:1133-44

Inaba K, Masui S, IidaH, Vavassori S, Sitia R., Suzuki M (2010). Crystal structures of human Ero1α reveal the mechanisms of regulated and targeted oxidation of PDI. EMBO J 29:3330-43

Venè R, Delfino L, Castellani P, Balza E, Bertolotti M, Sitia R., Rubartelli A (2010). Redox remodeling allows and controls B cell activation and differentiation. Antioxid. Redox Signal, vol. in press.

Ronzoni R. Anelli T, Brunati M, Cortini M, Fagioli C and Sitia R. 2010. Pathogenesis of ER Storage Disorders:modulating Russell Body biogenesis by altering proximal and distal quality control Traffic, 11(7):947-57

Anelli T and Sitia R. 2010 Physiology and pathology of proteostasis in the early secretory compartment. Semin Cell Dev Biol. 21:520-5

Cortini M and Sitia R. 2010. ERp44 and ERGIC-53 synergize in coupling efficiency and fidelity of IgM polymerization and secretion. Traffic, 11; 651-659

Rubartelli A and Sitia R. 2009 Chemo-metabolic regulation of immune responses by Tregs. Nature Chem- Biol. 10, 709-1

Bianchi G, Oliva L, Cascio P, Pengo N, Fontana F, Cerruti F, Orsi A, Pasqualetto E, Mezghrani A, Calbi V, Palladini G, Giuliani N, Anderson KC, Sitia R°, Cenci S°. 2009 The proteasome load vs. capacity balance determines apoptotic sensitivity of multiple myeloma cells to proteasome inhibition. Blood. 113, 3040-9. °joint last authors
Rubartelli A and Sitia R. 2009 Stress as an intercellular signal: the emergence of stress associated molecular patterns (SAMP). Antioxid Redox Signal. 11, 2621-9

Wang L°, Wang L°, Vavassori S°, Li S, Ke H, Anelli T, Degano M, Ronzoni R, Sitia R§, Sun F§ & Wang CC§ 2008. Crystal structure of human ERp44 reveals a dynamic functional modulation by its C-terminal tail. EMBO Rep. 9, 642-7. §/°joint last/first authors

Fraldi A°, Zito E°, Annunziata F, Lombardi A, Cozzolino M, Monti M, Spampanato C, Ballabio A, Pucci P,Sitia R§ and Cosma P § 2008. Multistep, sequential control of the trafficking and function of the multiple sulfatase deficiency gene product, SUMF1 by PDI, ERGIC-53 and ERp44. Hum. Molec. Gen. 17, 2610-2 §/°joint last/first authors

Nerini-Molteni S, Ferrarini M, Cozza S, Caligaris-Cappio F and Sitia R. 2008. Redox homeostasis modulates the sensitivity of myeloma cells to proteasome inhibitors. Brit. J. Haemat., 41, 494-503.

Cascio P, Oliva L, Cerruti F, Mariani E, Pasqualetto E, Cenci S, Sitia R. (2008) Dampening Ab responses using proteasome inhibitors following in vivo B cell activation. Eur J Immunol. 38(3):658-67

Anelli T and Sitia R. 2008. Protein quality control in the early secretory pathway. EMBO J. 27, 315-27.

Anelli T, Ceppi S, Bergamelli L, Cortini M, Masciarelli S, Valetti C and Sitia R. 2007 Sequential steps and checkpoints in the early exocytic compartment during secretory IgM biogenesis. EMBO J. 26, 4177-88

Cenci, S., Mezghrani, A., Cascio, P., Bianchi, G., Cerruti, F., Fra, A., Lelouard, H., Masciarelli, S., Mattioli, L., Oliva, L., Orsi, A., Pasqualetto, E., Pierre, P., Ruffato, E., Tagliavacca, L. and Sitia, R. (2006) Progressively impaired proteasomal capacity during terminal plasma cell differentiation. EMBO J, 25, 1104-1113.

Orsi A, Fioriti L, Chiesa R, Sitia R 2006 Conditions of endoplasmic reticulum stress favor the accumulation of cytosolic prion protein. J Biol Chem 281, 30431-8

Sitia R, Nerini-Molteni SN. 2004 Stress, protein (mis)folding, and signaling: the redox connection. Science STKE. 239, 27.

Sitia R and Braakman I. (2003). Quality control in the endoplasmic reticulum protein factory. Nature 426, 891-4.

VanAnken E, Romijn EP, Maggioni C, Mezghrani A, Sitia R§, Braakman I§, and Heck AJR§ (2003) Sequential waves of functionally related proteins are expressed when B cells prepare for antibody secretion. Immunity 18, 243-53. §joint last authors

Anelli T., Alessio M., Mezghrani A., Simmen T., Talamo F., Bachi A., Sitia R. (2002) ERp44, a novel endoplasmic reticulum folding assistant of the thioredoxin family. EMBO J. 21, 835.

Mezghrani A., Fassio A., Benham A., Simmen T., Braakman I., Sitia R. (2001). Manipulation of Oxidative Protein Folding and PDI Redox State in Mammalian Cells. EMBO J. 20, 6288.
Project Title:
Integrating Protein Transport and Signalling at the ER-Golgi Interface
Quality control at the ER-Golgi interface ensures fidelity of the secretory proteome (Anelli & Sitia, 2008). The multifunctional chaperone ERp44 retains incompletely assembled intermediates: it also binds and regulates the oxidase Ero1α and the Ca2+ channel IP3-Receptor 1, linking protein quality control to Ca2+ and redox homeostasis/signalling. ERp44 is regulated by the ER-Golgi pH gradient (see Figure below). Silencing the Golgi pH regulator (GpHR) allows secretion of proteins normally retained by ERp44. GpHR silencing inhibits cytodieresis. We aim to further dissect ERp44 regulation and the consequences of altering the pH in the early secretory compartment (ESC).

Experimental strategy
Isolate novel ERp44 interactors by co-IP with available engineered mutants. Determine their subcellular localisation and function.

Analyse how GpHR silencing impairs cell division.
Verify the generality of the phenomenon silencing or overexpressing GPHR mutants in different cell types. Map domains or motifs involved.

Understanding how protein transport and signalling are coregulated in ESC may improve production of proteins of biomedical interest and lead to novel therapies for conformational or ER storage diseases (Anelli & Sitia, 2010; Cenci, van Anken & Sitia, 2011).

Project Title:
Proteostasis and redoxtasis as therapeutic targets against multiple myeloma and other plasma cell discrasias
Exuberant protein secretion induces endoplasmic reticulum (ER) and oxidative stress, since protein folding generates H2O2 (Masciarelli & Sitia, 2008). H2O2 could be secreted or transported to the cytosol, acting as inter- or intra- cellular signaling devices (Rubartelli & Sitia, 2009, see figure below). This issue is particularly relevant in oncology, because for tyrosine kinase signals to act, topologically restrained phosphatase inhibition by H2O2 is essential. Additional H2O2 sources induce NOX enzymes and mitochondria (Margittai & Sitia, 2011). Also proteasomal load and capacity, key determinants of the sensitivity of myeloma cells to proteasome inhibitors, are redox-regulated (Nerini et al., 2008; Bianchi et al., 2009). Thus, we aim to further explore how redoxtasis control the differentiation, activity and life-span of antibody secreting cells cells. This approach is of relevance in the treatment of myeloma and possibly other secretory malignancies.

Experimental strategy
-Express organelle-targeted GFP-based redox and H2O2 sensors in myeloma cells with different sensitivity to proteasome inhibitors, and follow H2O2 diffusion before and after drug treatment. Link the results to ongoing protein synthesis and iron homeostasis
-Use Ero1 inhibitors to reduce H2O2 production in the ER
-Determine if H2O2 diffuses across membranes and/or is secreted and its role as an intra- or inter-cellular signaling device.
Understanding how proteostasis and redoxtasis impact signaling can identify novel targets in plasma cell malignancies. or