Les Krushel Associate Professor Ph.D., University of Toronto, 1990 Phone: (303) 724-3646 leslie.krushel@ucdenver.edu

My lab is interested in the mechanisms and regulation of protein synthesis in neurons and how these translational mechanisms contribute to neural processes such as learning and memory. Protein synthesis occurs in mammalian dendrites and is required for particular physiological models of learning and memory. Local protein synthesis in dendrites may provide a mechanism for a rapid and a spatially restricted translational response to neural activity. Indeed, recent evidence suggests that newly synthesized proteins are necessary at the synapse in order for changes in synaptic efficacy to occur. For example, additional neurotransmitter receptors could produce a stronger postsynaptic response to the same stimulus.

In my lab, we are determining the mechanisms of translation in dendrites and how these mechanisms are regulated by synaptic events. Most eukaryotic mRNAs are thought to initiate translation by the translational machinery binding the cap structure and scanning to the first initiator codon. However, in some mRNAs an alternative mechanism of initiating translation can occur in which the translational machinery binds to a segment of the mRNA (usually the 5' untranslated region (UTR)) rather than to the cap. The segment is generally referred to as an internal ribosome entry site (IRES). We have recently demonstrated that the 5' UTRs of five dendritically localized mRNAs exhibit IRES activity and that translation in dendrites occurs by both cap and IRES dependent mechanisms (Pinkstaff et al., 2001).

The present research in my lab focuses on identifying novel IRESes and determining their contribution to neural functions. Analysis of IRES activity occurs in three phases:

1. Identification of novel IRES elements. We are examining whether IRES-dependent translation is restricted to a particular class of neural mRNAs (e.g. dendritically localized) or whether it is a general translational mechanism for all neural mRNAs.


2. Analysis of translation in neuronal dendrites. We are studying in vitro the cellular conditions that stimulate cap and IRES dependent translation in neuronal cell bodies and in dendrites. For example, does neural activity lead to an increase in protein synthesis in dendrites and by what translational mechanism?


3. Determining the mechanisms for IRES-dependent translation. We are dissecting the 5' UTR's to ascertain the sequences responsible for the internal initiation of translation. We are also isolating the trans-acting proteins that bind to the IRES to determine their contribution to translation regulation.

Newer projects in the laboratory focus on the roles of internal initiation of translation in human disease, including cancer, Alzheimer’s disease and Fragile-X syndrome.

Veo BL, Krushel LA. Translation initiation of the human tau mRNA through an internal ribosomal entry site.
J Alzheimers Dis. 2009 Feb;16(2):271-5.

Beaudoin ME, Poirel VJ, Krushel LA. Regulating amyloid precursor protein synthesis through an internal ribosomal entry site. Nucleic Acids Res. 2008 Dec;36(21):6835-47.

Dobson T, Kube E, Timmerman S, Krushel LA. Identifying intrinsic and extrinsic determinants that regulate internal initiation of translation mediated by the FMR1 5' leader. BMC Mol Biol. 2008 Oct 15;9:89.

Timmerman SL, Pfingsten JS, Kieft JS, Krushel LA. The 5' leader of the mRNA encoding the mouse neurotrophin receptor TrkB contains two internal ribosomal entry sites that are differentially regulated.  PLoS ONE. 2007 Sep 19;3(9):e3242.

Li PW, Li J, Timmerman SL, Krushel LA, Martin SL. The dicistronic RNA from the mouse LINE-1 retrotransposon contains an internal ribosome entry site upstream of each ORF: implications for retrotransposition. Nucleic Acids Res. 2006 Feb 6;34(3):853-64.

Dobson T, Minic A, Nielsen K, Amiott E, Krushel L. Internal initiation of translation of the TrkB mRNA is mediated by multiple regions within the 5' leader.
Nucleic Acids Res. 2005 May 20;33(9):2929-41.

Salbaum JM, Cirelli C, Walcott E, Krushel LA, Edelman GM, Tononi G. Chlorotoxin-mediated disinhibition of noradrenergic locus coeruleus neurons using a conditional transgenic approach. Brain Res. 2004 Jul 30;1016(1):20-32.

Pinkstaff JK, Chappell SA, Mauro VP, Edelman GM, Krushel LA. Internal initiation of translation of five dendritically localized neuronal mRNAs.  Proc Natl Acad Sci U S A. 2001 Feb 27;98(5):2770-5.

Little EB, Crossin KL, Krushel LA, Edelman GM, Cunningham BA. A short segment within the cytoplasmic domain of the neural cell adhesion molecule (N-CAM) is essential for N-CAM-induced NF-kappa B activity in astrocytes. Proc Natl Acad Sci U S A. 2001 Feb 27;98(5):2238-43.

Choi J, Krushel LA, Crossin KL. NF-kappaB activation by N-CAM and cytokines in astrocytes is regulated by multiple protein kinases and redox modulation. Glia. 2001 Jan;33(1):45-56.

Crossin KL, Krushel LA. Cellular signaling by neural cell adhesion molecules of the immunoglobulin superfamily. Dev Dyn. 2000 Jun;218(2):260-79. Review.

Vanderklish PW, Krushel LA, Holst BH, Gally JA, Crossin KL, Edelman GM. Marking synaptic activity in dendritic spines with a calpain substrate exhibiting fluorescence resonance energy transfer. Proc Natl Acad Sci U S A. 2000 Feb 29;97(5):2253-8.

Phillips GR, Krushel LA, Crossin KL. Domains of tenascin involved in glioma migration. J Cell Sci. 1998 Apr;111 ( Pt 8):1095-104.

Holst BD, Vanderklish PW, Krushel LA, Zhou W, Langdon RB, McWhirter JR, Edelman GM, Crossin KL. Allosteric modulation of AMPA-type glutamate receptors increases activity of the promoter for the neural cell adhesion molecule, N-CAM. Proc Natl Acad Sci U S A. 1998 Mar 3;95(5):2597-602.

Krushel LA, Tai MH, Cunningham BA, Edelman GM, Crossin KL.Neural cell adhesion molecule (N-CAM) domains and intracellular signaling pathways involved in the inhibition of astrocyte proliferation. Proc Natl Acad Sci U S A. 1998 Mar 3;95(5):2592-6.

Phillips GR, Krushel LA, Crossin KL. Developmental expression of two rat sialyltransferases that modify the neural cell adhesion molecule, N-CAM. Brain Res Dev Brain Res. 1997 Sep 20;102(2):143-55.

Crossin KL, Tai MH, Krushel LA, Mauro VP, Edelman GM. Glucocorticoid receptor pathways are involved in the inhibition of astrocyte proliferation. Proc Natl Acad Sci U S A. 1997 Mar 18;94(6):2687-92.

Wang Y, Krushel LA, Edelman GM. Targeted DNA recombination in vivo using an adenovirus carrying the cre recombinase gene. Proc Natl Acad Sci U S A. 1996 Apr 30;93(9):3932-6.

Wang Y, Jones FS, Krushel LA, Edelman GM. Embryonic expression patterns of the neural cell adhesion molecule gene are regulated by homeodomain binding sites.

Proc Natl Acad Sci U S A. 1996 Mar 5;93(5):1892-6.

Krushel LA, Sporns O, Cunningham BA, Crossin KL, Edelman GM. Neural cell adhesion molecule (N-CAM) inhibits astrocyte proliferation after injury to different regions of the adult rat brain. Proc Natl Acad Sci U S A. 1995 May 9;92(10):4323-7.

Hazan R, Krushel L, Crossin KL. EGF receptor-mediated signals are differentially modulated by concanavalin A. J Cell Physiol. 1995 Jan;162(1):74-85.

Krushel LA, Prieto AL, Edelman GM, Crossin KL. Differential effects of cytotactin/tenascin fusion proteins on intracellular pH and cell morphology. J Cell Physiol. 1994 Dec;161(3):508-18.

Mauro VP, Wood IC, Krushel L, Crossin KL, Edelman GM. Cell adhesion alters gene transcription in chicken embryo brain cells and mouse embryonal carcinoma cells. Proc Natl Acad Sci U S A. 1994 Mar 29;91(7):2868-72.