Regulation of the activity and cell surface expression of the neuronal glutamate transporter EAAC1 by multiple signaling pathways.

Format:

Book

Thesis/Dissertation

Author/Creator:

Sims, Karen Davis.

Contributor:

Robinson, Michael B., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Neurosciences.

0317.

Penn dissertations--Neuroscience.

Neuroscience--Penn dissertations.

Local Subjects:

Penn dissertations--Neuroscience.

Neuroscience--Penn dissertations.

0317.

Physical Description:

191 pages

Contained In:

Dissertation Abstracts International 60-12B.

System Details:

Mode of access: World Wide Web.

text file

Summary:

The primary mechanism for the removal of glutamate and aspartate from the extracellular space is a family of five sodium-dependent high affinity transporters. These transporters are selectively expressed in either neurons or glia, and may be critical for the limitation of excitotoxic injury following acute insults to the CNS. The neuronal transporter EAAC1 is of special interest because it is enriched in the hippocampus and cortex, two areas exquisitely sensitive to excitotoxic insults. In C6 glioma, a CNS-derived cell line that endogenously and selectively expresses the EAAC1 subtype of transporter, L-[ 3H]-glutamate transport activity was rapidly increased following phorbol 12-myristate 13-acetate (PMA)-induced activation of protein kinase C (PKC). This increase was correlated with an increase in cell surface EAAC1 immunoreactivity as measured by cell surface biotinylation, followed by batch extraction and Western blotting. The effects of PMA occurred within minutes and did not change total cellular EAAC1 immunoreactivity, implying no net synthesis or degradation of transporter occurred. A selective PKC inhibitor blocked both effects of PMA. Immunofluorescence confocal microscopy revealed that PMA treatment induced clustering of EAAC1 transporters on the cell surface.

The translocation of the GLUT4 subtype of glucose transporter has been studied extensively, and is primarily regulated by insulin activation of phosphatidylinositol 3-kinase (PI3-K). To determine if similar receptor-mediated events regulate the activity and cell surface expression of EAAC1, several growth factors were tested for effects on glutamate uptake activity. Only platelet-derived growth factor (PDGF) stimulated EAAC1-mediated transport activity within minutes, and was correlated with a rapid increase in EAAC1 cell surface expression. The effects of PDGF were accompanied by a 35-fold increase in PI3-K activity and were blocked by the PI3-K inhibitors wortmannin and LY294002, but not by an inhibitor of PKC. Wortmannin alone also decreased EAAC1-mediated transport activity and cell surface expression of the transporter within minutes, and induced transporter localization to a perinuclear vesicular compartment. Together, these data suggest that both the PKC and PI3-K pathways may independently regulate EAAC1 activity and cell surface expression. It is possible that PDGF-mediated increases in EAAC1 activity may contribute to previously demonstrated neuroprotective effects of PDGF.

Notes:

Thesis (Ph.D. in Neuroscience) -- University of Pennsylvania, 1999.

Source: Dissertation Abstracts International, Volume: 60-12, Section: B, page: 5964.

Adviser: Michael B. Robinson.

Local Notes:

School code: 0175.

ISBN:

9780599558625

Access Restriction:

Restricted for use by site license.