Tissue specific variants of glutamate transporter GLT‐1

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Abstract
CDNA cloning of glutamate transporter GLT‐1 from mouse brain and liver has revealed that 5′‐ends of the messages are different between brain and liver. In addition, one of the GLT‐1 cDNAs isolated from liver has been found to possess a 3′‐end different from those of the others. Reverse transcription polymerase chain reaction (RT‐PCR) amplification using primers specific for altered 5′‐ends has confirmed that brain and liver messages possess their own specific 5′‐ends. Both of the two 3′‐ends have been demonstrated by RT‐PCR to be present not only in liver but also in brain, indicating both brain and liver GLT‐1 possess two types of 3′‐ends. Although functional properties are not changed by the alteration of N‐termini and C‐termini when expressed in Xenopus laevis oocytes, co‐expression of two liver type GLT‐1 with different C‐termini (mGLT‐1A and mGLT‐1B) has been found to result in the increase in V max of transport without changing K m. These results suggest the tissue specific alternative splicing at 5′‐ends of GLT‐1 messages and the interesting association of spliced variants with different C‐termini.