Don B. Arnold
Molecular & Computational Biology
College of Letters Arts & Sciences
Phone: (213) 821-1266
RRI. Rm 208
- B.A.Sc. University of Toronto, 1986.
- Ph.D. John Hopkins University, 1992.
- Postdoctoral Fellow, Rockefeller University 1992-1997.
- Postdoctoral Fellow, Harvard University 1997-1999.
- Cellular Neurobiology
- Membranes & Transport
Research OverviewThe work in my laboratory is focused on two broad areas.
(1) We study the molecular mechanisms underlying polarized targeting of proteins in neurons. We have discovered an actin- and myosin-based mechanism by which transmembrane proteins such as ion channels and receptors are targeted to either the surface of the axon or to the somatodendritic compartment. We showed that interaction with Myosin Va is both necessary and sufficient for the localization of dendritic proteins and Myosin VI plays a similar role in localization of proteins to the surface of the axon. We also showed recently that vesicles carrying dendritic or axonal proteins enter axons and dendrites with equal frequencies immediately following release from the Golgi apparatus. In the axon initial segment, however, vesicles carrying dendritic proteins almost all halt and some reverse in an actin- and Myosin Va-dependent manner, while vesicles carrying axonal proteins proceed to the distal axon. These results suggest that an actin-dependent vesicle filter is present in the AIS that mediates the selective trafficking of vesicles depending on their contents.
(2) We have developed recombinant probes known as intrabodies that can be used to label endogenous proteins in living neurons, or to mediate the degradation of endogenous proteins inducibly, specifically and very quickly. To make intrabodies we use mRNA display, an in vitro selection procedure developed by our collaborator Richard Roberts. We have used intrabodies to report the localization of endogenous proteins in neurons in dissociated culture, as well as in slices and in vivo following in utero electroporation. We have made intrabodies against PSD95, Gephyrin, CAM Kinase II and Kv4.2. When expressed in neurons intrabodies accurately report the localization and trafficking of target proteins without affecting their localization, expression level or function. Modified intrabodies known as ablating intrabodies can mediate the degradation of their endogenous target proteins inducibly, specifically, and very quickly. Ablating intrabodies mediate the direct ablation of their target proteins and, thus, work much faster than traditional, nucleic acid-based methods of protein degradation, such as RNAi. Furthermore, intrabodies are capable of specifically degrading proteins in particular conformations or with specific post-translational modifications. Thus, they could be used to specifically degrade pathological proteins involved in neurodegenerative diseases such as Alzheimerís, Parkinsonís and Huntingtonís, without degrading wild-type forms of these proteins.
Al-Bassam, S., Xu, M., Wandless, T.J., and Arnold, D. B. Differential trafficking of transport vesicles contributes to localization of dendritic proteins. in press Cell Reports.
Arnold DB. (2009) Actin and microtubule-based cytoskeletal cues direct polarized targeting of proteins in neurons. Science Signaling, 2(83):pe49. -PubMed
Lewis TL Jr, Mao T, Svoboda K, Arnold DB. (2009) Myosin-dependent targeting of transmembrane proteins to neuronal dendrites. Nat Neurosci.12(5):568-576. -PubMed
Chu PJ, Rivera JF, Arnold DB. (2006) A role for Kif17 in transport of Kv4.2. J Biol Chem. 281(1):365-373. -PubMed
Arnold DB. (2007) Polarized targeting of ion channels in neurons. Pflugers Arch. 453(6):763-769. -PubMed
Rivera, J. F., Ahmad, S., Quick, M. W., Liman, E. R., and Arnold, D. B. (2003) An evolutionarily conserved dileucine motif in Shal K+ channels mediates dendritic targeting. Nat Neurosci. 6(3):243-250. -PubMed
Arnold DB. (1999) Clapham DE Molecular determinants for subcellular localization of PSD-95 with an interacting K+ channel. Neuron 23(1):149-157. -PubMed
Tao X, Finkbeiner S, Arnold DB, Shaywitz AJ, Greenberg ME. (1998) Ca2+ influx regulates BDNF transcription by a CREB family transcription factor-dependent mechanism. Neuron 20(4):709-726. -PubMed
Arnold DB, Heintz N. (1997) A calcium responsive element that regulates expression of two calcium binding proteins in Purkinje cells. Proc Natl Acad Sci USA 94(16):8842-8847. -PubMed