April 2009
Volume 50, Issue 13
ARVO Annual Meeting Abstract  |   April 2009
TRPV5, TRPV6 Expression in Retinal Pigment Epithelium
Author Affiliations & Notes
  • B. G. Kennedy
    Cellular and Integrative Physiology,
    Indiana Univ Sch of Medicine-Northwest, Gary, Indiana
  • A. J. Torabi
    Cellular and Integrative Physiology,
    Indiana Univ Sch of Medicine-Northwest, Gary, Indiana
  • S. F. Echtenkamp
    Cellular and Integrative Physiology,
    Indiana Univ Sch of Medicine-Northwest, Gary, Indiana
  • N. J. Mangini
    Anatomy & Cell Biology,
    Indiana Univ Sch of Medicine-Northwest, Gary, Indiana
  • Footnotes
    Commercial Relationships  B.G. Kennedy, None; A.J. Torabi, None; S.F. Echtenkamp, None; N.J. Mangini, None.
  • Footnotes
    Support  American Health Assistance Foundation Macular Degeneration Research
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 1859. doi:
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      B. G. Kennedy, A. J. Torabi, S. F. Echtenkamp, N. J. Mangini; TRPV5, TRPV6 Expression in Retinal Pigment Epithelium. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1859.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : : Hydration and ionic composition of the subretinal space is modulated by retinal pigment epithelial (RPE) transport activity. In particular, calcium concentration in the subretinal space (SRS) varies with light exposure. Although this change is modulated by the RPE, the specific transport proteins involved have yet to be defined. TRPV5 and TRPV6 are calcium selective ion channels known to be expressed in calcium transporting epithelial tissues. The present work characterizes expression of TRPV5 and TRPV6 in RPE.

Methods: : : Immunocytochemistry was employed to determine expression and subcellular localization of TRPV5 and TRPV6 in frozen, formaldehyde-fixed sections of native RPE/choroid and in cultured human RPE monolayers. Expression was also assessed by western blot analysis. Finally transcript identity was determined by PCR analysis.

Results: : : Immunohistochemical analysis showed that both TRPV5 and TRPV6 are expressed in native RPE/choroid preparations. Immunoreactivity was detected for both channels on the apical as well as the basal plasma membranes. Immunostaining for both channels was also positive in monolayers of cultured RPE cells. In cultured cells staining was predominantly present in the cytoplasmic domain. Expression was further documented by western blot analysis. The reported molecular weight of the glycosylated proteins is in the range of 85-100 kD. For TRPV6 in the RPE a distinct band was detected at 85 kD with another strong band at ~60 kD. A similar pattern was seen for TRPV5 with strong bands at 82 and 71 kD. PCR analysis of native and cultured RPE documented the presence of transcripts for both TRPV5 and TRPV6. Identity of the transcripts was confirmed by sequencing.

Conclusions: : : The RPE expresses the epithelial calcium channels TRPV5 and TRPV6. These are the most calcium selective channels of the TRP superfamily and could function in RPE to mediate calcium influx from SRS. These channels exhibit a distinct mode for functional regulation which entails insertion into the plasma membrane. It will be determined if changes in SRS composition associated with light onset regulate channel insertion into the RPE plasma membrane.

Keywords: retinal pigment epithelium • calcium • ion channels 

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