Tissue plasminogen activator alters intracellular sequestration of zinc through interaction with the transporter ZIP4

J Neurosci. 2010 May 12;30(19):6538-47. doi: 10.1523/JNEUROSCI.6250-09.2010.

Abstract

Glutamatergic neurons contain free zinc packaged into neurotransmitter-loaded synaptic vesicles. Upon neuronal activation, the vesicular contents are released into the synaptic space, whereby the zinc modulates activity of postsynaptic neurons though interactions with receptors, transporters and exchangers. However, high extracellular concentrations of zinc trigger seizures and are neurotoxic if substantial amounts of zinc reenter the cells via ion channels and accumulate in the cytoplasm. Tissue plasminogen activator (tPA), a secreted serine protease, is also proepileptic and excitotoxic. However, tPA counters zinc toxicity by promoting zinc import back into the neurons in a sequestered form that is nontoxic. Here, we identify the zinc influx transporter, ZIP4, as the pathway through which tPA mediates the zinc uptake. We show that ZIP4 is upregulated after excitotoxin stimulation of the mouse, male and female, hippocampus. ZIP4 physically interacts with tPA, correlating with an increased intracellular zinc influx and lysosomal sequestration. Changes in prosurvival signals support the idea that this sequestration results in neuroprotection. These experiments identify a mechanism via which neurons use tPA to efficiently neutralize the toxic effects of excessive concentrations of free zinc.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Cation Transport Proteins / metabolism*
  • Cell Line
  • Cells, Cultured
  • Female
  • Hippocampus / drug effects
  • Hippocampus / metabolism*
  • Humans
  • In Vitro Techniques
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism*
  • Lysosomes / drug effects
  • Lysosomes / metabolism
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Neurons / drug effects
  • Neurons / metabolism*
  • Neurotoxins / toxicity
  • Tissue Plasminogen Activator / deficiency
  • Tissue Plasminogen Activator / genetics
  • Tissue Plasminogen Activator / metabolism*
  • Zinc / metabolism*

Substances

  • Cation Transport Proteins
  • Neurotoxins
  • Slc39a4 protein, mouse
  • Tissue Plasminogen Activator
  • Zinc