Gregg G. Gundersen, PhD
Research in my laboratory is focused on the fundamental question of how cells generate cellular asymmetry to carry out their specific function. Elements of the cytoskeleton, known as microtubules, have been found to play a central role in this process.
We utilize motile fibroblasts as a model system to study how microtubules contribute to cell polarity. In these cells there are two sources of microtubule polarity: the selective stabilization of microtubules oriented towards the leading edge, and the reorientation of microtubule organizing center (MTOC) towards the leading edge. We are currently investigating how the polarization of the microtubule array is signaled in the cytoplasm, and how the polarization of the microtubule array contributes to other cell polarity processes. We employ biochemical, molecular and cell biological approaches to address these questions, including real time microscopic observation of the behavior of fluorescent molecules introduced into cells by microinjection or by transfection.
The stabilization of microtubules in specific locations in cells is central to the idea that microtubules drive cellular polarization. We have developed a serum starved fibroblast system to identify extracellular factors and intracellular signal transduction pathways involved in triggering microtubule stabilization in crawling fibroblasts. We have used this system to show that the small GTP-binding protein, Rho, a member of the ras superfamily, is critically involved in the selective stabilization of microtubules in the lamella of crawling cells. Recently we identified the mDia, a member of the formin family of proteins, as the downstream target of Rho that mediates MT stabilization. In budding yeast formins have been genetically implicated in the capture and shrinkage of the plus end of microtubules in the cortex of the bud. We are currently testing whether other proteins from the "capture shrinkage pathway" (i.e. EB1 and APC) are involved in microtubule stabilization in fibroblasts.
The subunit protein of microtubules, tubulin, undergoes a unique post translation modification, known as detyrosination, when microtubules are stabilized. We have recently found that detyrosination acts as a signal for the interaction of stable microtubules with other organelles in the cell. Thus, detyrosinated microtubules act as preferential sites for the establishment of an extended array of vimentin intermediate filaments in fibroblasts. In addition, detyrosinated microtubules are preferentially used for export from the endocytic recycling compartment while tyrosinated microtubules are are preferentially used for import from the plasma membrane to this compartment. Other cellular organelles, e.g., mitochondria and endoplasmic reticulum, may also be dependent on detyrosinated microtubules. With these results, we are now able to suggest a general mechanism for how cells establish internal organization: 1) dynamic microtubules are locally stabilized 2) the stable microtubules are post-translationally modified, and 3) the modified microtubules interact with other cellular organelles.
Recently we used the serum starved fibroblast system to show that MTOC reorientation is regulated by a specific signal transduction pathway. Similar to the microtubule stabilization pathway, MTOC reorientation is triggered by a small G-protein, CDC42. By activating MTOC orientation with serum factors or active CDC42 we have been able to determine that dynein and the dynactin complex act downstream of CDC42 to provide the force required to reposition the MTOC in response to extracellular cues. Importantly we have shown that MTOC reorientation and selective stabilization of microtubules towards the cell edge are each controlled by distinct and independent signaling pathways despite the fact that these two polarization events act to rearrange a single microtubule array.
In the final project in the laboratory, we have begun to analyze the relationship between adhesion and microtubules. We plan to address two questions: how adhesion affect the microtubule stabilization pathway, and how microtubule dynamics affect focal adhesion turnover.
Chang W, Antoku S, Gundersen GG. Wound-Healing Assays to Study Mechanisms of Nuclear Movement in Fibroblasts and Myoblasts. Methods Mol Biol 2016; 1411:255-67(Pubmed)
Nader GP, Ezratty EJ, Gundersen GG. FAK, talin and PIPKIγ regulate endocytosed integrin activation to polarize focal adhesion assembly. Nat Cell Biol 2016 May; 18(5):491-503(Pubmed)
Wang Y, Lichter-Konecki U, Anyane-Yeboa K, Shaw JE, Lu JT, Östlund C, Shin JY, Clark LN, Gundersen GG, Nagy PL, Worman HJ. Mutation abolishing the ZMPSTE24 cleavage site in prelamin A causes a progeroid disorder. J Cell Sci2016 Mar 31; pii: jcs.187302(Pubmed)
Bartolini F, Andres-Delgado L, Qu X, Nik S, Ramalingam N, Kremer L, Alonso MA, Gundersen GG. An mDia1-INF2 formin activation cascade facilitated by IQGAP1 regulates stable microtubules in migrating cells. Mol Biol Cell 2016 Mar 30; pii: mbc.E15-07-0489(Pubmed)
Arsenovic PT, Ramachandran I, Bathula K, Zhu R, Narang JD, Noll NA, Lemmon CA, Gundersen GG, Conway DE. Nesprin-2G, a Component of the Nuclear LINC Complex, Is Subject to Myosin-Dependent Tension. Biophys J 2016 Jan 5;110(1):34-43(Pubmed)
Li Y, Lovett D, Zhang Q, Neelam S, Kuchibhotla RA, Zhu R, Gundersen GG, Lele TP, Dickinson RB. Moving Cell Boundaries Drive Nuclear Shaping during Cell Spreading. Biophys J 2015 Aug 18;109(4):670-86(Pubmed)
Antoku S, Zhu R, Kutscheidt S, Fackler OT, Gundersen GG. Reinforcing the LINC complex connection to actin filaments: the role of FHOD1 in TAN line formation and nuclear movement. Cell Cycle 2015;14(14):2200-5(Pubmed)
Reversat A, Yuseff MI, Lankar D, Malbec O, Obino D, Maurin M, Penmatcha NV, Amoroso A, Sengmanivong L, Gundersen GG, Mellman I, Darchen F, Desnos C, Pierobon P, Lennon-Duménil AM. Polarity protein Par3 controls B-cell receptor dynamics and antigen extraction at the immune synapse. Mol Biol Cell 2015 Apr 1;26(7):1273-85(Pubmed)
Chang W, Antoku S, Östlund C, Worman HJ, Gundersen GG. Linker of nucleoskeleton and cytoskeleton (LINC) complex-mediated actin-dependent nuclear positioning orients centrosomes in migrating myoblasts. Nucleus 2015;6(1):77-88(Pubmed)
Chang W, Worman HJ, Gundersen GG. Accessorizing and anchoring the LINC complex for multifunctionality. J Cell Biol 2015 Jan 5;208(1):11-22 (Review)(Pubmed)
Meinke P, Mattioli E, Haque F, Antoku S, Columbaro M, Straatman KR, Worman HJ, Gundersen GG, Lattanzi G, Wehnert M, Shackleton S. Muscular dystrophy-associated SUN1 and SUN2 variants disrupt nuclear-cytoskeletal connections and myonuclear organization. PLoS Genet 2014 Sep 11;10(9):e1004605(Pubmed)
Kutscheidt S, Zhu R, Antoku S, Luxton GW, Stagljar I, Fackler OT, Gundersen GG. FHOD1 interaction with nesprin-2G mediates TAN line formation and nuclear movement. Nat Cell Biol 2014 Jul;16(7):708-15(Pubmed)
Morris EJ, Nader GP, Ramalingam N, Bartolini F, Gundersen GG. Kif4 interacts with EB1 and stabilizes microtubules downstream of Rho-mDia in migrating fibroblasts. PLoS One 2014 Mar 21;9(3):e91568(Pubmed)
Shahbazi MN, Megias D, Epifano C, Akhmanova A, Gundersen GG, Fuchs E, Perez-Moreno M. CLASP2 interacts with p120-catenin and governs microtubule dynamics at adherens junctions. J Cell Biol 2013 Dec 23;203(6):1043-61(Pubmed)
Sabo Y, Walsh D, Barry DS, Tinaztepe S, de Los Santos K, Goff SP, Gundersen GG, Naghavi MH. HIV-1 induces the formation of stable microtubules to enhance early infection. Cell Host Microbe 2013 Nov 13;14(5):535-46(Pubmed)
Chang W, Folker ES, Worman HJ, Gundersen GG. Emerin organizes actin flow for nuclear movement and centrosome orientation in migrating fibroblasts. Mol Biol Cell 2013 Dec;24(24):3869-80(Pubmed)
Naghavi MH, Gundersen GG, Walsh D. Plus-end tracking proteins, CLASPs, and a viral Akt mimic regulate herpesvirus-induced stable microtubule formation and virus spread. Proc Natl Acad Sci U S A 2013 Nov 5;110(45):18268-73(Pubmed)
Gundersen GG, Worman HJ. Nuclear positioning. Cell 2013 Mar 14;152(6):1376-89 (Review)(Pubmed)