Tuning of the Outer Hair Cell Motor by Membrane Cholesterol

Rajagopalan, Lavanya; Greeson, Jennifer N.; Xia, Anping; Liu, Haiying; Sturm, Angela; Raphael, Robert M.; Davidson, Amy L.; Oghalai, John S.; Pereira, Fred A.; Brownell, William E.

doi:10.1074/jbc.m705078200

Cited by 96 publications

(144 citation statements)

References 83 publications

(38 reference statements)

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“…On a pragmatic level, recent reports have associated hyperlipidemia and dyslipidemia with hearing loss (47,48). The findings that outer hair cell function is tuned to membrane cholesterol content (49,17) further strengthens the growing evidence suggesting that membrane lipid microdomains may be important for hair cell physiology and pathophysiology.…”

Section: Discussionsupporting

confidence: 57%

Plasticity in Membrane Cholesterol Contributes toward Electrical Maturation of Hearing

Levic

Yamoah

2011

Journal of Biological Chemistry

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Section: Discussionsupporting

confidence: 57%

Plasticity in Membrane Cholesterol Contributes toward Electrical Maturation of Hearing

Levic

Yamoah

2011

Journal of Biological Chemistry

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“…2A). Since prestin is present in membrane microdomains and several biochemical and functional properties of prestin are modulated by membrane cholesterol (Sturm et al 2006;Rajagopalan et al 2007), we determined if glycosylation plays a role in membrane distribution in altered cholesterol environments. Prestin NN163/166AA has a punctate distribution in the membrane, similar to WT prestin, in untreated cells ( Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The lateral wall of the adult OHC is low in cholesterol (Santi et al 1994;Nguyen and Brownell 1998;Oghalai et al 1999;Brownell and Oghalai 2000;Rajagopalan et al 2007). This may have an impact on the modulation of prestin function, as recent observations indicate a direct and dynamic link between membrane cholesterol levels and prestin's functional and biochemical properties (Sturm et al 2006;Rajagopalan et al 2007). Matsuda et al (2004) showed that prestin is glycosylated in several cell lines and OHCs and identified residues N163 and N166 to be glycosylated.…”

Section: Introductionmentioning

confidence: 99%

“…N-glycosylation of proteins is an important post-translational covalent modification that has been implicated in protein folding, sorting and trafficking, and importantly, membrane and raft localization of proteins (Huet et al 2003;Fullekrug and Simons 2004). Based on the propensity of prestin to localize to cholesterol-rich membrane microdomains (Sturm et al 2006;Rajagopalan et al 2007), we investigated the possible role of glycosylation in membrane raft localization and trafficking of prestin. Our results indicate a functional and regulatory role for glycosylation in the cellular trafficking and/or internalization, particularly cholesterol-induced endocytosis, of prestin.…”

Section: Introductionmentioning

confidence: 99%

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Glycosylation Regulates Prestin Cellular Activity

Rajagopalan

Darling

Liu

et al. 2009

JARO

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Glycosylation is a common post-translational modification of proteins and is implicated in a variety of cellular functions including protein folding, degradation, sorting and trafficking, and membrane protein recycling. The membrane protein prestin is an essential component of the membrane-based motor driving electromotility changes (electromotility) in the outer hair cell (OHC), a central process in auditory transduction. Prestin was earlier identified to possess two N-glycosylation sites (N163, N166) that, when mutated, marginally affect prestin nonlinear capacitance (NLC) function in cultured cells. Here, we show that the double mutant prestin NN163/166AA is not glycosylated and shows the expected NLC properties in the untreated and cholesterol-depleted HEK 293 cell model. In addition, unlike WT prestin that readily forms oligomers, prestin NN163/166AA is enriched as monomers and more mobile in the plasma membrane, suggesting that oligomerization of prestin is dependent on glycosylation but is not essential for the generation of NLC in HEK 293 cells. However, in the presence of increased membrane cholesterol, unlike the hyperpolarizing shift in NLC seen with WT prestin, cells expressing prestin NN163/166AA exhibit a linear capacitance function. In an attempt to explain this finding, we discovered that both WT prestin and prestin NN163/166AA participate in cholesterol-dependent cellular trafficking. In contrast to WT prestin, prestin NN163/166AA shows a significant cholesterol-dependent decrease in cellsurface expression, which may explain the loss of NLC function. Based on our observations, we conclude that glycosylation regulates self-association and cellular trafficking of prestin NN163/166AA . These observations are the first to implicate a regulatory role for cellular trafficking and sorting in prestin function. We speculate that the cholesterol regulation of prestin occurs through localization to and internalization from membrane microdomains by clathrin-and caveolin-dependent mechanisms.

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“…However, the magnitude of cholesterol-induced effects was reduced in HEKs as compared to OHCs. Previous studies using fluorescent labels suggested that the cholesterol concentration of the OHC lateral plasma membrane is significantly less than in the apical or basal regions (Nguyen and Brownell 1998;Oghalai et al 1998;Rajagopalan et al 2007), so small changes in absolute cholesterol concentration in this region may have a significant effect on membrane material properties and membrane-protein interactions.…”

Section: Discussionmentioning

confidence: 97%

Lipid Lateral Mobility in Cochlear Outer Hair Cells: Regional Differences and Regulation by Cholesterol

Organ

Raphael

2009

JARO

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The outer hair cell (OHC) lateral plasma membrane houses the transmembrane protein prestin, a necessary component of the yet unknown molecular mechanism (s) underlying electromotility and the exquisite sensitivity and frequency selectivity of mammalian hearing. The importance of the plasma membrane environment in modulating OHC electromotility has been substantiated by recent studies demonstrating that membrane cholesterol alters prestin activity in a manner consistent with cholesterol-induced changes in auditory function. Cholesterol is known to affect membrane material properties, and measurements of lipid lateral mobility provide a method to asses these changes in living OHCs. Using fluorescence recovery after photobleaching (FRAP), we characterized regional differences in the lateral diffusion of the lipid analog di-8-ANEPPS in OHCs and investigated whether lipid mobility, which reflects membrane fluidity, is sensitive to membrane cholesterol. FRAP experiments revealed quantitative differences in lipid lateral mobility among the apical, lateral, and basal regions of the OHC and demonstrated that diffusion in individual regions is uniquely sensitive to cholesterol manipulations. Interestingly, in the lateral region, both cholesterol depletion and loading significantly reduced the effective diffusion coefficient from control values. Thus, the fluidity of the OHC lateral plasma membrane is regulated by cholesterol levels in a non-monotonic manner, suggesting that the overall material properties of the lateral plasma membrane are optimally tuned for OHC function in the native state. These results support the idea that the cholesteroldependent regulation of prestin function and electromotility correlates with changes in the properties of the lipid environment that surrounds and supports prestin.

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Tuning of the Outer Hair Cell Motor by Membrane Cholesterol

Cited by 96 publications

References 83 publications

Plasticity in Membrane Cholesterol Contributes toward Electrical Maturation of Hearing

Plasticity in Membrane Cholesterol Contributes toward Electrical Maturation of Hearing

Glycosylation Regulates Prestin Cellular Activity

Lipid Lateral Mobility in Cochlear Outer Hair Cells: Regional Differences and Regulation by Cholesterol

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