Identification and characterization of two novel splice forms of GRIP1 in the rat brain

• Published in: Journal of neurochemistry 2006-05, Vol.97 (3), p.884-898
• Main Authors: Charych, Erik I, Li, Rongwen, Serwanski, David R, Li, Xuejing, Miralles, Celia P, Pinal, Noelia, De Blas, Angel L
• Format: Article
• Language: English
• Subjects: Alternative Splicing - genetics; Amino Acid Sequence; Animals; Biochemistry and metabolism; Biological and medical sciences; Blotting, Northern - methods; Brain - cytology; Brain - metabolism; Brain - ultrastructure; Brain research; Carrier Proteins - genetics; Carrier Proteins - metabolism; Cells, Cultured; Central nervous system; Cloning; Cloning, Molecular - methods; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Disks Large Homolog 4 Protein; Electron microscopes; electron microscopy; Embryo, Mammalian; Fundamental and applied biological sciences. Psychology; GABAergic synapse; Glutamate Decarboxylase - metabolism; glutamate receptor interacting protein 1; Hippocampus - cytology; immunocytochemistry; Immunohistochemistry - methods; Intracellular Signaling Peptides and Proteins - metabolism; Medical sciences; Membrane Proteins - metabolism; Microscopy, Immunoelectron - methods; Molecular Weight; Nerve Tissue Proteins - genetics; Nerve Tissue Proteins - metabolism; Neurology; Neurons - cytology; Neurons - metabolism; Neurosciences; Oligonucleotide Array Sequence Analysis - methods; PDZ domain; postsynaptic density; Protein Isoforms - genetics; Protein Isoforms - metabolism; Rats; Rats, Sprague-Dawley; Rodents; Sequence Alignment - methods; Synapses - metabolism; Synapses - ultrastructure; Vertebrates: nervous system and sense organs; Vesicular Glutamate Transport Protein 1 - metabolism
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2006.03795.x

We cloned two novel alternatively-spliced mRNA isoforms of glutamate receptor interacting protein 1 (GRIP1) which we named GRIP1d and GRIP1e 4-7. GRIP1d is a 135 kDa, 7-PDZ-domain variant of GRIP1, containing the 12 amino acid C-terminus originally described for the 4-PDZ-domain GRIP1c 4-7. GRIP1e 4-7 is a 75 kDa 4-PDZ-domain variant of GRIP1, containing the 12 amino acid C-terminus originally described for the 7-PDZ-domain GRIP1a/b. Northern blots indicated that GRIP1d mRNA is 5.1 kb long and abundant in brain. An antibody to the C-terminus of the 75 kDa GRIP1c 4-7 also recognized an abundant 135 kDa protein, consistent with the predicted size of GRIP1d. Similarly, an antibody to the C-terminus of the 135 kDa GRIP1a/b also recognized a low abundance 75 kDa protein, consistent with the predicted size of GRIP1e 4-7. Immunocytochemistry of hippocampal cultures and intact brain using these antibodies showed that (i) these isoforms are present in both GABAergic and glutamatergic synapses, and (ii) the isoforms co-localize in individual synapses. While GRIP1a/b isoforms are abundant in interneurons and highly concentrated in GABAergic presynaptic terminals, the isoforms recognized by the antibody to the C-terminus common to GRIP1c 4-7 and GRIP1d are much less abundant in interneurons and preferentially concentrate at the postsynaptic complex.