Tissue specific variants of glutamate transporter GLT-1

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 Vmax of transport without changing Km. 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.