Numerous G protein-coupled receptors (GPCRs) are glycosylated at extracellular regions. The regulatory roles of glycosylation on receptor function vary across receptor types. In this study, we used the dopamine D₂and D₃receptors as an experimental model to understand the underlying principles governing the functional roles of glycosylation. We used the pharmacological inhibitor, tunicamycin, to inhibit glycosylation, generated chimeric D₂and D₃receptors by swapping their respective N-termini, and produced the glycosylation site mutant D₂and D₃receptors to study the roles of glycosylation on receptor functions, including cell surface expression, signaling, and internalization through specific microdomains. Our results demonstrate that glycosylation on the N-terminus of the D₃ receptor is involved in the development of desensitization and proper cell surface expression. In addition, glycosylation on the N-terminus mediates the internalization of D₂and D₃receptors within the caveolae and clathrin-coated pit microdomains of the plasma membrane, respectively, by regulating receptor interactions with caveolin-1 and clathrin. In conclusion, this study shows for the first time that glycosylation on the N-terminus of GPCRs is involved in endocytic pathway selection through specific microdomains. These data suggest that changes in the cellular environment that influence posttranslational modification could be an important determinant of intracellular GPCR trafficking.
This paper proposes an on/off control of boost power factor correction (PFC) converters to improve the light-load efficiency in paralleled power supply units (PSUs) for servers. The proposed scheme operates the PFC stages of two paralleled PSUs alternately during one cycle of a 60-Hz ac input only at light loads. This improves the light-load efficiency without deteriorating the heavy-load efficiency by reducing load-independent losses such as capacitive turn-on and core losses. In addition, the proposed scheme alleviates the harmonic distortion by reducing the discontinuous conduction mode region. Experimental results from 1.6-kW PFC boost converters are shown to verify the proposed work.Index Terms-Boost converter, light-load efficiency, on/off control, paralleled power supply units (PSUs), power factor correction (PFC), servers.
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