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Expression of the mouse macrophage cystine transporter in Xenopus laevis oocytes
1Institute of Basic Medical Sciences, University of Tsukuba, Japan.
Abstract:
System xc- mediates transport of cystine and glutamate across the mammalian plasma membrane in a Na(+)-independent manner. This transport activity can be induced in mouse peritoneal macrophages during culture by diethylmaleate, a sulfhydryl-reactive agent. We injected mRNA from such macrophages into Xenopus oocytes and demonstrated the expression of System xc-, i.e., a Na(+)-independent, glutamate-inhibitable cysteine transport system. The expressed cystine transport activity depended on the assay temperature, in that cystine uptake measured at 37 degrees C was severalfold higher than that measured at 20 degrees C. Injection of size-fractionated mRNA indicated that the System xc- transporter of the mouse macrophage is encoded by mRNA of 1.5 to 2.9 kb.
Insights
Researchers identified the mRNA encoding the mouse macrophage System xc- transporter. This system facilitates cystine and glutamate transport and is crucial for cellular functions, with its expression dependent on mRNA size.
Area of Science:
- Molecular biology
- Cellular physiology
- Biochemistry
Background:
- System xc- is a mammalian plasma membrane transporter for cystine and glutamate.
- Its transport activity is Na(+)-independent.
- Diethylmaleate induces System xc- activity in mouse peritoneal macrophages.
Purpose of the Study:
- To demonstrate the expression of functional System xc- in Xenopus oocytes.
- To characterize the properties of the expressed transporter.
- To identify the mRNA size encoding the System xc- transporter.
Main Methods:
- Injection of mRNA from induced mouse peritoneal macrophages into Xenopus oocytes.
- Assay of Na(+)-independent, glutamate-inhibitable cystine transport.
- Size fractionation of mRNA and subsequent expression analysis.
Main Results:
- Functional System xc- was expressed in Xenopus oocytes.
- Expressed cystine transport was temperature-dependent, higher at 37°C than 20°C.
- The transporter is encoded by mRNA between 1.5 and 2.9 kb.
Conclusions:
- System xc- transporter from mouse macrophages can be functionally expressed in Xenopus oocytes.
- The molecular size of the mRNA encoding this transporter was determined.
- This study provides insights into the molecular basis of cystine-glutamate transport.