The iodide-transport-defect-causing mutation R124H: A δ-amino group at position 124 is critical for maturation and trafficking of the Na+/I- symporter

Viktoriya Paroder, Juan P. Nicola, Christopher S. Ginter, Nancy Carrasco

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Na+/I- symporter (NIS)-mediated active accumulation of I- in thyrocytes is a key step in the biosynthesis of the iodine-containing thyroid hormones T3 and T4. Several NIS mutants have been identified as a cause of congenital I- transport defect (ITD), and their investigation has yielded valuable mechanistic information on NIS. Here we report novel findings derived from the thorough characterization of the ITD-causing mutation R124H, located in the second intracellular loop (IL-2). R124H NIS is incompletely glycosylated and colocalizes with endoplasmic reticulum (ER)-resident protein markers. As a result, R124H NIS is not targeted to the plasma membrane and therefore does not mediate any I- transport in transfected COS-7 cells. Strikingly, however, the mutant is intrinsically active, as revealed by its ability to mediate I- transport in membrane vesicles. Of all the amino acid substitutions we carried out at position 124 (K, D, E, A, W, N and Q), only Gln restored targeting of NIS to the plasma membrane and NIS activity, suggesting a key structural role for the δ-amino group of R124 in the transporter's maturation and cell surface targeting. Using our NIS homology model based on the structure of the Vibrio parahaemolyticus Na+/galactose symporter, we propose an interaction between the d-amino group of either R or Q124 and the thiol group of C440, located in IL-6. We conclude that the interaction between IL-2 and IL-6 is critical for the local folding required for NIS maturation and plasma membrane trafficking.

Original languageEnglish (US)
Pages (from-to)3305-3313
Number of pages9
JournalJournal of Cell Science
Volume126
Issue number15
DOIs
StatePublished - 2013

Fingerprint

Symporters
Iodides
Mutation
Cell Membrane
1,1,1,2-tetrafluoro-2-chloroethane
Interleukin-2
Interleukin-6
Vibrio parahaemolyticus
COS Cells
Triiodothyronine
Amino Acid Substitution
Galactose
Thyroxine
Sulfhydryl Compounds
Iodine
Endoplasmic Reticulum

Keywords

  • Congenital iodide transport defect
  • Impaired intracellular trafficking
  • Membrane vesicles
  • Na/I symporter (NIS)
  • Plasma membrane targeting

ASJC Scopus subject areas

  • Cell Biology

Cite this

The iodide-transport-defect-causing mutation R124H : A δ-amino group at position 124 is critical for maturation and trafficking of the Na+/I- symporter. / Paroder, Viktoriya; Nicola, Juan P.; Ginter, Christopher S.; Carrasco, Nancy.

In: Journal of Cell Science, Vol. 126, No. 15, 2013, p. 3305-3313.

Research output: Contribution to journalArticle

Paroder, Viktoriya ; Nicola, Juan P. ; Ginter, Christopher S. ; Carrasco, Nancy. / The iodide-transport-defect-causing mutation R124H : A δ-amino group at position 124 is critical for maturation and trafficking of the Na+/I- symporter. In: Journal of Cell Science. 2013 ; Vol. 126, No. 15. pp. 3305-3313.
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T1 - The iodide-transport-defect-causing mutation R124H

T2 - A δ-amino group at position 124 is critical for maturation and trafficking of the Na+/I- symporter

AU - Paroder, Viktoriya

AU - Nicola, Juan P.

AU - Ginter, Christopher S.

AU - Carrasco, Nancy

PY - 2013

Y1 - 2013

N2 - Na+/I- symporter (NIS)-mediated active accumulation of I- in thyrocytes is a key step in the biosynthesis of the iodine-containing thyroid hormones T3 and T4. Several NIS mutants have been identified as a cause of congenital I- transport defect (ITD), and their investigation has yielded valuable mechanistic information on NIS. Here we report novel findings derived from the thorough characterization of the ITD-causing mutation R124H, located in the second intracellular loop (IL-2). R124H NIS is incompletely glycosylated and colocalizes with endoplasmic reticulum (ER)-resident protein markers. As a result, R124H NIS is not targeted to the plasma membrane and therefore does not mediate any I- transport in transfected COS-7 cells. Strikingly, however, the mutant is intrinsically active, as revealed by its ability to mediate I- transport in membrane vesicles. Of all the amino acid substitutions we carried out at position 124 (K, D, E, A, W, N and Q), only Gln restored targeting of NIS to the plasma membrane and NIS activity, suggesting a key structural role for the δ-amino group of R124 in the transporter's maturation and cell surface targeting. Using our NIS homology model based on the structure of the Vibrio parahaemolyticus Na+/galactose symporter, we propose an interaction between the d-amino group of either R or Q124 and the thiol group of C440, located in IL-6. We conclude that the interaction between IL-2 and IL-6 is critical for the local folding required for NIS maturation and plasma membrane trafficking.

AB - Na+/I- symporter (NIS)-mediated active accumulation of I- in thyrocytes is a key step in the biosynthesis of the iodine-containing thyroid hormones T3 and T4. Several NIS mutants have been identified as a cause of congenital I- transport defect (ITD), and their investigation has yielded valuable mechanistic information on NIS. Here we report novel findings derived from the thorough characterization of the ITD-causing mutation R124H, located in the second intracellular loop (IL-2). R124H NIS is incompletely glycosylated and colocalizes with endoplasmic reticulum (ER)-resident protein markers. As a result, R124H NIS is not targeted to the plasma membrane and therefore does not mediate any I- transport in transfected COS-7 cells. Strikingly, however, the mutant is intrinsically active, as revealed by its ability to mediate I- transport in membrane vesicles. Of all the amino acid substitutions we carried out at position 124 (K, D, E, A, W, N and Q), only Gln restored targeting of NIS to the plasma membrane and NIS activity, suggesting a key structural role for the δ-amino group of R124 in the transporter's maturation and cell surface targeting. Using our NIS homology model based on the structure of the Vibrio parahaemolyticus Na+/galactose symporter, we propose an interaction between the d-amino group of either R or Q124 and the thiol group of C440, located in IL-6. We conclude that the interaction between IL-2 and IL-6 is critical for the local folding required for NIS maturation and plasma membrane trafficking.

KW - Congenital iodide transport defect

KW - Impaired intracellular trafficking

KW - Membrane vesicles

KW - Na/I symporter (NIS)

KW - Plasma membrane targeting

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