Apolipoprotein A-I increases association of cytosolic cholesterol and caveolin-1 with microtubule cytoskeletons in rat astrocytes

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Abstract

Apolipoprotein (apo) A-I induces rapid translocation of protein kinase Cα and phospholipase Cγ, and slow translocation of caveolin-1 and newly synthesized cholesterol to the cytosolic lipid-protein particle (CLPP) fraction in rat astrocytes. In order to understand the function of CLPP, we investigated the interaction with cytoskeletons of CLPP-related proteins such as caveolin-1 and protein kinase Cα and of CLPP-related lipids in rat astrocytes. Under the conditions that microtubules were depolymerized, association of cytosolic caveolin-1 with protein kinase Cα and α-tubulin was enhanced when the cells were treated with apoA-I for 5 min. This association was suppressed by a scaffolding domain-peptide of caveolin-1. Association with the microtubule-like filaments of cytosolic lipids, caveolin-1 and protein kinase Cα was also increased by the apoA-I treatment and inhibited by the scaffolding domain peptide. Paclitaxel (taxol), a compound to stabilize microtubules, suppressed the apoA-I-mediated intracellular translocation and release from the cells of the de novo synthesized cholesterol and phospholipid. The findings suggested that the association of CLPP with microtubules is mediated by a scaffolding domain of caveolin-1, induced by apoA-I and involved in regulation of intracellular cholesterol trafficking for assembly of cellular lipids to apoA-I–high-density lipoprotein (HDL).

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