Regulation of the high-affinity H+/peptide cotransporter in renal LLC-PK1 cells

✍ Scribed by Uwe Wenzel; Daniela Diehl; Martina Herget; Sabine Kuntz; Hannelore Daniel

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 187 KB
• Volume: 178
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/(sici)1097-4652(199903)178:3<341::aid-jcp8>3.0.co;2-h

✦ Synopsis

Di-and tripeptides and peptide mimetics such as ␤-lactam antibiotics are efficiently reabsorbed from the tubular lumen by a high-affinity peptide transporter. We have recently identified and characterized this H ϩ -coupled high-affinity peptide transport system in the porcine proximal tubular cell line LLC-PK 1 . Here we describe for the first time the regulation of the renal high-affinity peptide cotransporter at the cellular level. Uptake of 5 M 3 H-D-Phe-L-Ala into LLC-PK 1 cells was significantly increased by lowering [Ca 2ϩ ] in and decreased by increasing [Ca 2ϩ ] in . Moreover, it was shown that the [Ca 2ϩ ] in effects on peptide transport activity were dependent on Ca 2ϩ entry from the extracellular site (e.g., via a store-regulated capacitative Ca 2ϩ influx). Protein kinase C (PKC) was found to transmit the effects of [Ca 2ϩ ] in on peptide transport. Although we demonstrate by pH in measurements that the PKC inhibitor staurosporine did decrease the transmembrane H ϩ gradient and consequently should have reduced the driving force for peptide uptake, the only effect on transport kinetics of 3 H-D-Phe-L-Ala observed was a significant decrease in K m from 22.7 Ϯ 2.5 M to 10.2 Ϯ 1.9 M with no change in maximal velocity.