IQGAP-2: a novel interacting partner with the human colonic thiamin pyrophosphate transporter

Kalidas Ramamoorthy, Subrata Sabui, George Kim, James M. Flekenstein, Alaullah Sheikh, Hamid M. Said

Research output: Contribution to journalArticlepeer-review

Abstract

The human colonic thiamin pyrophosphate transporter (hcTPPT) mediates the uptake of the microbiota-generated and phosphorylated form of vitamin B1 (i.e., thiamin pyrophosphate) in the large intestine. Expression of hcTPPT along the absorptive tract is restricted to the large intestine, and the transporter is exclusively localized at the apical membrane domain of the polarized epithelial cells/colonocytes. Previous studies have characterized different physiological/pathophysiological aspects of the hcTPPT system, but nothing is currently known on whether the transporter has interacting partner(s) that affect its physiology/biology. We addressed this issue using a Y2H to screen a human colonic cDNA library and have identified three putative interactors, namely IQGAP-2, SNX-6, and DMXL-1. Focusing on IQGAP-2 (whose expression in human colonocytes is the highest), we found (using fluorescent microscopy imaging and coimmunoprecipitation approaches) the putative interactor to colocalize with hcTPPT and to directly interact with the transporter. Also, overexpressing IQGAP-2 in NCM460 cells and in human primary differentiated colonoid monolayers was found to lead to significant (P < 0.01) induction in TPP uptake, while knocking down (using gene-specific siRNAs) caused significant (P < 0.01 and P < 0.05) decrease in uptake. Furthermore, overexpressing IQGAP-2 in NCM460 cells was found to lead to a significant enhancement in hcTPPT protein stability. Finally, we found the expression of IQGAP-2 to be markedly suppressed in conditions/factors that negatively impact colonic TPP uptake. These results identify the IQGAP-2 as an interacting partner with the hcTPPT in human colonocytes and show that this interaction has physiological and biological consequences.

Original languageEnglish
Pages (from-to)C1451-C1461
JournalAmerican Journal of Physiology - Cell Physiology
Volume327
Issue number6
DOIs
StatePublished - Dec 2024

Keywords

  • accessory proteins
  • colonic uptake
  • human colonocytes
  • IQGAP-2
  • thiamin pyrophosphate

Fingerprint

Dive into the research topics of 'IQGAP-2: a novel interacting partner with the human colonic thiamin pyrophosphate transporter'. Together they form a unique fingerprint.

Cite this