Rene Harrison

We have a cell biology lab that focusses on immune and bone cells. We study macrophage activation and the cellular machinery behind enhanced phagocytosis and pathogen clearance in activated macrophages. We also study all the major bone cell types: osteoblasts, osteoclasts and osteocytes. Using cell culture and advanced microscopy we are trying to understand how these cell types modulate the bone matrix in normal and in diseased conditions, such as osteoporosis. 

Research Synopsis

Our cell biology laboratory is located in the Science Wing at the University of Toronto Scarborough (UTSC). The lab is equipped with modern cell and molecular biology infrastructure and is a Biosafety Level II laboratory for the work on pathogen modulation manipulation of infected host cells. We have a Zeiss epifluorescent microscope encaged in a CO2 incubator with temperature control to allow long-term imaging of living cells. Dr. Harrison is also administers the Centre for the Neurobiology of Stress facility and UTSC and her lab uses all of the fluorescent (spinning disk confocal) and electron (transmission and scanning) microscopes within the facility.        

Our CIHR-funded work has focused on the microtubule (MT) cytoskeleton, specifically in macrophages that are important cells of the innate immune system.

1. Mechanism of FcgammaR and Mac-1-mediated Phagocytosis in Macrophages. Our lab has examined the MT contribution to two distinct types of phagocytosis. We determined that MTs function as a scaffold for PI3kinase at the phagocytic cup to mediate localized phosphoinositide metabolism necessary for membrane remodeling during FcR-mediated phagocytosis (Khandani et al., 2007). We showed that these MTs are targeted and stabilized at the phagocytic cup through the MT (+)-end binding protein, CLIP-170 (Binker et al., 2007). This was the first study demonstrating that CLIP-170 had a MT stabilizing role. We then went on to show that these stabilized subsets of MTs act as a tethering device to move the MT organizing centre (MTOC) towards the site of engaged FcR receptors (Eng et al., 2007). Moreover, the coordinated movement of the Golgi complex with the MTOC was important for understanding antigen presentation in macrophages. Finally, we showed that MTs are targeted to the phagocytic cup to facilitate directed trafficking of endomembranes, via the kinesin MT motor (Silver and Harrison, 2011). Intracellular membrane delivery and exocytosis is essential for phagocytic cup elaboration around IgG-opsonized particles, and this work identified the molecular machinery driving this transport event. Our studies of the MT requirements for Mac-1 mediated phagocytosis led to the finding that MT-induced membrane ruffles capture complement-opsonized particles (Patel and Harrison, 2008). This study was significant as it challenged the dogma that internalization of complement-opsonized particles was a ‘passive’ process, and active membrane protrusions have since been demonstrated for the uptake of IgG-coated targets (Flannagan et al., 2010).
2. Mechanism and Function of Stabilized Microtubules (MTs) in Activated Macrophages. Our MT analysis of macrophages also revealed that MTs are dramatically stabilized during macrophage classical activation (Binker et al., 2007; Hanania et al., 2012). We sought to identify the mechanism of MT stabilization and did an exhaustive study to elucidate the MT proteome in resting and activated macrophages (Patel et al., 2009). As this was the first published mammalian interphase MT proteome, this work also serves as an important database for other cytoskeleton researchers. Importantly, we wanted to determine the role of the global MT stabilization in activated macrophages. Activated macrophages are recruited to infected tissues, and we demonstrated that MT stabilization and kinesin activity was necessary for the robust MMP-9 trafficking and secretion that occurs when macrophages are exposed to inflammatory mediators (Hanania et al., 2012). Recently, we have shown that stathmin is a key protein that is down-regulated to induce MT stabilization in activated macrophages (Xu and Harrison, 2015).
3. Osteoblast (OB) and Osteoclast (OC) Function in Normal & Diseased Conditions. Our NSERC-funded studies of OBs centered on how collagen is mobilized and sorted intracellularly, within this major bone-producing cell. We identified the precise Rab GTPases (Nabavi et al., 2012), and the role of lysosome degradation (Nabavi et al., 2008), required for collagen production during OB differentiation and recently a role for EB1 and cell confluence and MTs in OB differentiation (Pustylnik et al., 2013) . We also had the opportunity to grow these cells for 2 weeks in microgravity, aboard the Foton M3; launched by the Russian Space Agency and funded by the CSA. We did detailed cellular analysis of these cells and discovered that the OB cytoskeleton and adhesion was markedly disrupted in microgravity-flown cells, compared to ground controls (Nabavi et al., 2011). In this study we also observed a surprising increase in bone resorption by OCs experiencing microgravity. Together these results explained the marked bone loss experienced by astronauts in microgravity and provided important insight into the mechanism behind disuse osteoporosis on earth. Through a CIHR-NET funded grant, we also determined that blood OC precursor cells have a higher potential to differentiate into OCs in patients with rheumatoid and osteo-arthritis (Durand et al., 2011; Durand et al., 2013).

Recent Publications

Selected list of publications

Weidner J.M., Kanatani S., Uchtenhagen H., Varas-Godoy M., Schulte T., Engelberg K., Gubbels M.J.,  Sun H.S., Harrison R.E., Achour A. and Barragan A. 2016.  Migratory activation of parasitized dendritic cells by the protozoan Toxoplasma gondii 14-3-3 protein. Cell. Microbiol. Mar 28. doi: 10.1111/cmi.12595.

Fiorino C. and Harrison R.E. 2016. E-cadherin cell contacts initiate osteoclastogenesis. Bone. 86:106-118. 

Sun H.S., Sin A., Poirier M. and Harrison R.E. 2016. Chlamydia trachomatis  inclusion disrupt host cell mitosis to enhance its growth in multinuclear cells. J. Cell Biochem.  117(1):132-43.

Xu K. and Harrison R.E. 2015. Down-regulation of stathmin is required for the phenotypic changes and classical activation of macrophages. J. Biol. Chem. 290(31): 19245-60.

Jeganathan S., Fiorino C., Naik U., Sun H.S. and Harrison R.E. 2014. Modulation of osteoclastogenesis with macrophage M1- and M2-inducing stimuli. PLoS ONE 9(8): e104498.

Pustylnik S.*, Fiorino C.*, Nabavi N., Zapatelli T., da Silva R. and Harrison R.E. 2013. EB1 levels are elevated in AA-stimulated osteoblasts and mediate cell-cell adhesion induced osteoblast differentiation. J. Biol. Chem. 288(30):22096-110. *contributed equally.

Durand M., Komarova S.V., Bhargava A., Trebec-Reynolds D.P., Li K., Fiorino C., Maria O., Nabavi N., Manolson M.F., Harrison R.E., Dixon S.J., Sims S.M., Mizianty M., Kurgan L., Haroun S., Boire G., Lucena-Fernandes M. and de Brum-Fernandes A.J. 2013. Monocytes from patients with osteoarthritis display increased osteoclastogenesis and bone resorption: The In Vitro Osteoclast Differentiation in Arthritis study. Arthritis and Rheumatism. 65(1):148-58.  *article highlighted in Issue.

Nabavi N., Pustylnik S. and Harrison R.E. 2012. RabGTPase mediated procollagen trafficking in ascorbic acid stimulated osteoblasts. PLoS One. 7(9):e46265. 

Sun H.S.*, Eng E.*, Jeganathan S., Sin A.T., Patel P.C., Gracey E., Inman R.D., Terebiznik M. and Harrison R.E. 2012. Chlamydia  trachomatis vacuole maturation in infected macrophages. J. Leukoc. Bio. 92(4):815-27.*contributed equally.

Hanania R., Sun H.S., Xu K., Pustylnik S., Jeganathan S. and Harrison R.E. 2012. Classically activated macrophages use stable microtubules for matrix metalloproteinase-9 (MMP-9) secretion. J. Biol. Chem. 287(11): 8468-83.

Sun H.S., Wilde A. and Harrison R.E. 2011. Chlamydia trachomatis inclusions induce asymmetric cleavage furrow formation and ingression failure in host cells. Mol. Cell. Biol. 31(24):5011-22. *featured on cover of 32(20) issue, 2012.

Nabavi N., Khandani A., Camirand A. and Harrison R.E. 2011. Effects of microgravity on osteoclast bone resorption and osteoblast cytoskeletal organization and adhesion. Bone. 49(5):965-74.

Silver K. and Harrison R.E. 2011. Measuring immune receptor mobility by fluorescence recovery after photobleaching. Methods Mol. Biol. 748:155-167.

Silver K. and Harrison R.E. 2011. Kinesin is involved in membrane trafficking to the pseudopod for efficient IgG-particle binding. J. Immunology. 186(2):816-25. *featured on cover.