The endoplasmic reticulum (ER) performs a number of functions essential for eukaryotic life. Principally, the ER is the site for the synthesis and translocation of all secretory and membrane proteins and thus represents the entry point to the secretory pathway. Coupled to this is a key function in protein folding and assembly, where nascent proteins interact with ER resident molecular chaperones to achieve their native structure and activity. These two aspects of ER function are integrated in the unfolded protein response pathway, which serves critical roles in cell stress, cell growth and cell differentiation.
   My laboratory has focused its research efforts on two topics: understanding how eukaryotic cells compartmentalize and regulate the protein synthesis activities of the cytosol and ER, and identifying the cellular, tissue, organ and organismal functions of the ER chaperone GRP94, the ER paralog of Hsp90, whose expression is essential for, and restricted to, multicellular eukaryotes. Regarding the former, we have recently reported that ER-bound ribosomes engage in the synthesis of secretory, integral and cytosolic proteins alike and that, surprisingly, mRNAs encoding cytosolic proteins can be highly partitioned to, and translated on, ER-bound ribosomes. We have also discovered that ribosome exchange on the ER is coupled to the translation of subsets of mRNAs. From these initial findings, we are working to understand the rules that govern ribosome and mRNA partitioning between the cytosol and ER of higher eukaryotic cells. These studies identify a new paradigm for defining the signals that govern the localization and trafficking dynamics of ribosomes and mRNA molecules in the cell.
  As a component of our research on protein translocation/protein translation, we have initiated studies on the regulation of ribosome and mRNA trafficking on the ER membrane during cell stress and recovery. As is now well established, cells subjected to stress conditions such as oxygen or nutrient deprivation undergo a stress response in which global protein synthesis is attenuated and resident ER chaperone synthesis activated. What cellular mechanisms are responsible for maintaining ER chaperone synthesis and translocation when global protein synthesis is inhibited? The overall aim of these studies is to develop an integrated physiological perspective on the regulation of ribosome and mRNA trafficking during cell stress and recovery.
  Molecular chaperones are a family of (poly)peptide binding proteins that assist in protein folding and assembly. The ER harbors an array of chaperones including GRP170, GRP94, the ER Hsp90 chaperone, GRP78(BiP), an ER Hsp70 chaperone, protein disulfide isomerase, calreticulin and others. In a fascinating and unanticipated development, GRP94 (gp96, ERp99, endoplasmin), has been also demonstrated to function as tumor rejection antigen. Thus, when isolated from tumor tissue, GRP94, can function as an immunotherapeutic vaccine against its tumor tissue of origin. What is the mechanism by which GRP94 can elicit cellular immune responses? To address this primary question, we are utilizing biochemical, cell biological and immunological methods to define the regulation of GRP94 (poly)peptide binding activity, the recognition and processing of GRP94 by the immune system and the molecular mechanism of GRP94-dependent tumor rejection. These studies embrace a broad methodology, and include atomic structure studies on GRP94 domains, biochemical and biophysical analyses of GRP94 structure/function relationships; cell biological analyses of GRP94 trafficking, and immunological studies of GRP94 function in the regulation of cellular immune responses.

E-mail
c.nicchitta@cellbio.duke.edu

366 Nanaline Duke Bldg., Box 3709
Duke University Medical Center
Durham, NC 27710

Telephone
919-684-8948 (office)
919-684-8980 (lab)
Fax 919-684-5481

New Postdoc Position Available

Pyhtila et al. Nuclear Envelope Micrograph

Selected Publications
Yewdell JW, Nicchitta CV. (2006) The DRiP hypothesis decennial: support, controversy, refinement and extension. Trends Immunol. 2006 27(8):368-73. -PDF-

Chu F, Maynard JC, Chiosis G, Nicchitta CV, Burlingame AL. (2006) Identification of novel quaternary domain interactions in the Hsp90 chaperone, GRP94. Protein Sci. 15(6):1260-9.

Lerner RS, Nicchitta CV. (2006) mRNA translation is compartmentalized to the endoplasmic reticulum following physiological inhibition of cap-dependent translation. RNA. 12(5):775-789. -PDF-

Stephens, S.B., Dodd, R.D., Brewer, J.W., Lager, P.J., Keene, J.D., and Nicchitta, CV. (2005) Stable Ribosome Binding to the Endoplasmic Reticulum Enables Compartment-Specific Regulation of mRNA Translation. Mol. Biol. Cell 16(12):5819-31. -PDF-

Liu S, Wang H, Yang Z, Kon T, Zhu J, Cao Y, Li F, Kirkpatrick J, Nicchitta CV, Li CY. (2005) Enhancement of cancer radiation therapy by use of adenovirus-mediated secretable glucose-regulated protein 94/gp96 expression. Cancer Res.65(20):9126-31.

Nicchitta, CV., Lerner, R.S., Stephens, S.B., Dodd, R.D., and Pyhtila, B. (2005) Pathways for compartmentalizing protein synthesis in eukaryotic cells: The Template Partitioning Model. Mol. Cell. Biochem. 83(6):687-695. -PDF-

Nicchitta CV, Carrick DM, Baker-Lepain JC. (2004) The messenger and the message: gp96 (GRP94)-peptide interactions in cellular immunity. Cell Stress Chaperones. 2004 9(4):325-31.

Baker-LePain JC, Sarzotti M, Nicchitta CV. (2004) Glucose-regulated protein 94/glycoprotein 96 elicits bystander activation of CD4(+) T cell Th1 cytokine production in vivo. J Immunol. 2004;172(7):4195-203.

Rosser MF, Trotta BM, Marshall MR, Berwin B, Nicchitta CV. (2004) Adenosine nucleotides and the regulation of GRP94-client protein interactions. Biochemistry. 43(27):8835-45.

Berwin B, Hart JP, Rice S, Gass C, Pizzo SV, Post SR, Nicchitta CV. (2003) Scavenger receptor-A mediates gp96/GRP94 and calreticulin internalization by antigen-presenting cells. EMBO J. 2003 22(22):6127-36. -PDF-

Soldano KL, Jivan A, Nicchitta CV, Gewirth DT. (2003) Structure of the N-terminal domain of GRP94. Basis for ligand specificity and regulation. J Biol Chem. 278(48):48330-8.

Lerner, R.S., Seiser, R.M., Zheng, T., Lager, P.J., Reedy, M.C., Keene, J.D., Nicchitta, C.V. (2003) Partitioning and translation of mRNAs encoding soluble proteins on membrane-bound ribosomes. RNA. 9(9):1123-37.

Current Projects
Protein synthesis regulation:
  How is ribosome binding to the ER membrane regulated?
  What role does protein synthesis play in the regulation of ribosome binding and release on the ER?
  How is the protein synthesis activity of ER-bound ribosomes regulated during normal and stress conditions?
  What is the mechanism of mRNA targeting to, and release from, the ER membrane?
  Do (subclasses of) mRNAs contain ER-directed localization information?

Chaperone Function:
  How are GRP94 interactions with polypeptide substrates regulated?
  What is the identity of the GRP94 "proteome"? (those proteins whose functional expression requires GRP94).
  Are there cellular scenarios wherein GRP94 undergoes regulated release from the cell?
  How is GRP94 recognized by the cells of the immune system?
  What is the subcellular trafficking itinerary of GRP94 in antigen presenting cells?

Lab Personnel
Rebecca Dodd (Graduate student)
J. Taylor Herbert (MD/PhD student)
Angela Jockheck (Graduate student)
Joshua Lacsina (MD/PhD student)
Jason Maynard (Graduate student)
Lyudmila Kadyrova (Post-doctoral Fellow)
Tianli Zheng (Research Analyst)