Alternatively spliced three novel transcripts of gria1 in the cerebellum and cortex of mouse brain.

Glutamate receptor type 1 (GluR1) subunit of α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptors plays an important role in the expression of long-term potentiation and memory formation. GluR1 is encoded by gria1 gene containing 16 exons and 15 introns in mouse. Previous studies have reported two alternatively spliced variants of this subunit. These flip and flop variants differ enormously in their properties as well as expression. In our studies, we report the presence of three new transcripts of this gene present in the cerebellum and cortex of mouse brain produced by alternative splicing at 5' end. Four new exons are reported; N1 is located in 5' untranslated region, N2 is located in the 1st intronic region while N3 and N4 are located in the 2nd intronic region. The properties of these new exons encoding N-terminal variants are highly diverse. N1, N3 and N4 are coding while N2 is a non-coding exon and results in a truncated transcript. The existence of N2 exon containing transcript is further supported by the presence of an Expressed Sequence Tag from the database. The translated amino acid sequences of these transcripts differ in the presence of signal peptide as well as in their phosphorylation and acetylation pattern. The differences in their properties might be involved in receptor modulation.