Essential role of the zinc transporter ZIP9/SLC39A9 in regulating the activations of Akt and Erk in B-cell receptor signaling pathway in DT40 cells

PLoS One. 2013;8(3):e58022. doi: 10.1371/journal.pone.0058022. Epub 2013 Mar 7.

Abstract

The essential trace element zinc is important for all living organisms. Zinc functions not only as a nutritional factor, but also as a second messenger. However, the effects of intracellular zinc on the B cell-receptor (BCR) signaling pathway remain poorly understood. Here, we present data indicating that the increase in intracellular zinc level induced by ZIP9/SLC39A9 (a ZIP Zrt-/Irt-like protein) plays an important role in the activation of Akt and Erk in response to BCR activation. In DT40 cells, the enhancement of Akt and Erk phosphorylation following BCR activation requires intracellular zinc. To clarify this event, we used chicken ZnT5/6/7-gene-triple-knockout DT40 (TKO) cells and chicken Zip9-knockout DT40 (cZip9KO) cells. The levels of Akt and ERK phosphorylation significantly decreased in cZip9KO cells. In addition, the enzymatic activity of protein tyrosine phosphatase (PTPase) increased in cZip9KO cells. These biochemical events were restored by overexpressing the human Zip9 (hZip9) gene. Moreover, we found that the increase in intracellular zinc level depends on the expression of ZIP9. This observation is in agreement with the increased levels of Akt and Erk phosphorylation and the inhibition of total PTPase activity. We concluded that ZIP9 regulates cytosolic zinc level, resulting in the enhancement of Akt and Erk phosphorylation. Our observations provide new mechanistic insights into the BCR signaling pathway underlying the regulation of intracellular zinc level by ZIP9 in response to the BCR activation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens / immunology
  • Biological Transport
  • Cation Transport Proteins / genetics
  • Cation Transport Proteins / metabolism*
  • Cell Line
  • Chickens
  • Enzyme Activation
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • Gene Expression
  • Gene Knockout Techniques
  • Humans
  • Intracellular Space / metabolism
  • Phosphorylation
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Receptors, Antigen, B-Cell / immunology
  • Receptors, Antigen, B-Cell / metabolism*
  • Signal Transduction*
  • Zinc / metabolism*

Substances

  • Antigens
  • Cation Transport Proteins
  • Receptors, Antigen, B-Cell
  • Slc39a9 protein, human
  • Proto-Oncogene Proteins c-akt
  • Extracellular Signal-Regulated MAP Kinases
  • Zinc

Grants and funding

This work was supported in part by a consignment expense for the Molecular Imaging Research Programs entitled “Research Base for Exploring New Drugs” and “Kobe Cluster” from the Ministry of Education, Culture, Sports, Science and Technology of Japan (to SE), grants-in-aid from the Ministry of Education, Culture, Sports, Science, and Technology of Japan (to SE and TK), from the Ministry of Health, Labor, and Welfare of Japan for scientific research (to SE), the Kieikai Research Foundation (to TK), and The Salt Science Research Foundation (to SE and MH). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.