Abstract:
Fodrin or non erythroid spectrin is composed of an α (240kDa) and a β (235kDa)
subunit that form a tetrameric complex. It was isolated from goat brain as a part of
cytoplasmic gamma tubulin ring complex, which is the nucleating agent of microtubules
in mammalian cells. Gamma tubulin is present in cytoplasm as well as centrosomes but
it is from the centrosome that gamma tubulin ring complex nucleates microtubules. The
nucleation ability increases manifold for mitotic cells compared to interphase cells. In
order to study the role of fodrin on HEK293 cells that has very low amount of fodrin, we
overexpressed an α-fodrin EGFP plasmid in HEK293 cells. α-fodrin overexpression led
to an increase in the level of acetylated tubulin whereas the total tubulin or
gamma-tubulin amount remained the same. It has been earlier shown that the down
regulation of α-fodrin has effects on the cell cycle, specifically a G1-S arrest. In light of
this, cell cycle analysis upon overexpression of α-fodrin in HEK 293 cells revealed that
there was a shift towards S phase with simultaneous decrease in the G1 phase.
Besides, overexpression of α-fodrin led to a significant increase in the number of cells
with mitotic abnormalities in the form of unattached chromosomes. Analysis of the
spindle assembly checkpoint proteins revealed that the level of the protein MAD2 had
significantly reduced which possibly explained the chromosome detachment. Further, a
limited study showed a significant increase of gamma tubulin at the centrosomes when
α-fodrin was overexpressed.
