Title

Intracellular pH microdomains and RNA trafficking in oligodendrocytes

Date of Completion

January 2004

Keywords

Biology, Neuroscience|Biology, Cell

Degree

Ph.D.

Abstract

Intracellular pH (pHi) was measured in oligodendrocytes (OLs) using ratiometric pH indicator dye. The results indicate that OLs contain numerous alkaline pH microdomains in the perikaryon and proximal dendrites and acidic pH microdomains in distal dendrites. Alkaline pH microdomains are generated by the combined activities of Na+/H+ exchanger (NHE) and carbonic anhydrase II (CAII), whereas acidic pH microdomains are generated by activities of Na+/HCO3 cotransporter (NBC) and CAII. NHE is concentrated in the perikaryon and NBC and CAII are in most dendrites. Subcellular segregation of the three proteins results in the differential distribution of transport metabolons, which causes spatially non-uniform intracellular pH. ^ RNA trafficking in oligodendrocytes (OLs) involves directional movement along microtubules (MTs) using conventional kinesin. Time lapse analysis of RNA trafficking in OLs reveals velocity fluctuations during translocation in dendrites. Using an in vitro motility assay it was shown that, for conventional kinesin, MT binding decreases and velocity increases reciprocally with increasing pH from 6.4 to 7.4. Co-visualization of pH and RNA showed that RNA granules are co-localized with acidic pH microdomains. Furthermore, endogeneous RNA granules in OL were redistributed to the periphery of the cell at low pHi, while the perikaryon retention of RNA granules was observed at higher pHi. This study propose a mechanism whereby pHi microdomains regulate RNA trafficking in OLs by coordinating pH-dependence of motor activities. Acidic pH microdomains can attract RNAs. ^