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:
- 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.
- 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?
- 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.
Representative Publications:
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.
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