Neuronal and glial sodium-dependent transporters are crucial for the control of extracellular glutamate levels in the CNS. The regulation of these transporters is relatively unexplored, but the activity of other transporters is regulated by protein kinase C (PKC)-and phosphatidylinositol 3-kinase (PI3K)-mediated trafficking to and from the cell surface. In the present study the C6 glioma cell line was used as a model system that endogenously expresses the excitatory amino acid carrier 1 (EAAC1) subtype of neuronal glutamate transporter. As previously observed, phorbol 12-myristate 13-acetate (PMA) caused an 80% increase in transporter activity within minutes that cannot be attributed to the synthesis of new transporters. This increase in activity correlated with an increase in cell surface expression of EAAC1 as measured by using a membrane-impermeant biotinylation reagent. Both effects of PMA were blocked by the PKC inhibitor bisindolylmaleimide II (Bis II 3 H]-glycine transport. Wortmannin also decreased cell surface expression of EAAC1. Although wortmannin did not block the effects of PMA on activity, it prevented the PMA-induced increase in cell surface expression. This trafficking of EAAC1 also was examined with immunofluorescent confocal microscopy, which supported the biotinylation studies and also revealed a clustering of EAAC1 at cell surface after treatment with PMA. These studies suggest that the trafficking of the neuronal glutamate transporter EAAC1 is regulated by two independent signaling pathways and also may suggest a novel endogenous protective mechanism to limit glutamateinduced excitotoxicity.

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"Cutting" of actin filaments by villin was evaluated from the time course of filament depolymerization. Depolymerization was initiated by diluting polymerized actin, labeled with a fluorescent probe on either lysine-374 or cysteine-375, to a concentration well below the critical into a medium containing free villin and various concentrations of calcium (in addition to potassium and magnesium). It was observed that at high calcium concentrations (200 microM) the time course of depolymerization could not be described by the single exponential that defines it at low calcium and low villin levels. Instead, at high calcium, the exponent increased with time and the rate of depolymerization became greater than that of controls in the absence of villin. This contrasts with the inhibition of depolymerization by villin at low calcium. The latter inhibition is a consequence of the capping of the barbed filament end by villin as are the inhibition of filament elongation and the elevation of the critical concentration. Evidence is presented that the effects of villin at high calcium are the result of cutting of the actin filaments by villin. It thus appears that different calcium binding sites control capping and cutting and that the calcium binding sites regulating cutting have a much lower affinity for calcium than the sites regulating capping of the barbed filament ends.

BackgroundDelivery of a small for gestational age (SGA) infant has been associated with increased maternal risk of ischemic heart disease (IHD). It is uncertain whether giving birth to SGA infant is a specific determinant of later IHD, independent of other risk factors, or a marker of general poor health. The purpose of this study was to investigate the association between delivery of a SGA infant and maternal risk for IHD in relation to traditional IHD risk factors.Methods and FindingsRisk of maternal IHD was evaluated in a population based cross-sectional study of 6,608 women with a prior live term birth who participated in the National Health and Nutrition Examination Survey (1999–2006), a probability sample of the U.S. population. Sequence of events was determined from age at last live birth and at diagnosis of IHD. Delivery of a SGA infant is strongly associated with greater maternal risk for IHD (age adjusted OR; 95% CI: 1.8; 1.2, 2.9; p = 0.012). The association was independent of the family history of IHD, stroke, hypertension and diabetes (family history-adjusted OR; 95% CI: 1.9; 1.2, 3.0; p = 0.011) as well as other risk factors for IHD (risk factor-adjusted OR; 95% CI: 1.7; 1.1, 2.7; p = 0.025). Delivery of a SGA infant was associated with earlier onset of IHD and preceded it by a median of 30 (interquartile range: 20, 36) years.ConclusionsGiving birth to a SGA infant is strongly and independently associated with IHD and a potential risk factor that precedes IHD by decades. A pregnancy that produces a SGA infant may induce long-term cardiovascular changes that increase risk for IHD.