Characterization of the β2-microglobulin endocytic pathway in rat proximal tubule cells

David P. Sundin, Mark Cohen, Rolf Dahl, Sandor Falk, Bruce Molitoris

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

The uptake mechanism(s) of low-molecular-weight proteins by proximal tubule cells remains incompletely characterized. We utilized a biochemical and semiquantitative morphological approach to better characterize the endocytic pathway of an anionic protein, β2-microglobulin (β2M), in the rat proximal tubule. Indirect immunogold techniques revealed β2M was taken up via a classic receptor-mediated endocytic pathway. In vitro biochemical and morphological characterization of iodinated β2M and gold-conjugated β2M (gold-β2M) binding to isolated brush-border membrane vesicles (BBMV) documented specific and quantitatively similar binding Interactions of the modified β2M with BBMV. Kinetic characterization of the in vivo endocytic pathway of gold-β2M was undertaken using microinfusion of individual tubules. β2M initially bound at the apical surface, was internalized into subapical coated vesicles and delivered to endosomal-like structures within 5 min, and, finally, was concentrated in lysosomal-like structures within 15 min. This uptake was inhibited by excess unconjugated β2M. In addition, we directly showed that uptake did not occur across the basolateral surface. Finally, by passing solubilized BBMV over β2M affinity columns we were able to isolate binding activity.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Renal Fluid and Electrolyte Physiology
Volume267
Issue number3 36-3
StatePublished - Sep 1994
Externally publishedYes

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Microvilli
Gold
Membranes
Coated Vesicles
Proteins
Molecular Weight
Immunohistochemistry

Keywords

  • β-microglobulin modification
  • Low-molecular-weight protein uptake
  • Receptor isolation

ASJC Scopus subject areas

  • Physiology

Cite this

Characterization of the β2-microglobulin endocytic pathway in rat proximal tubule cells. / Sundin, David P.; Cohen, Mark; Dahl, Rolf; Falk, Sandor; Molitoris, Bruce.

In: American Journal of Physiology - Renal Fluid and Electrolyte Physiology, Vol. 267, No. 3 36-3, 09.1994.

Research output: Contribution to journalArticle

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