Antibodies to MAGI-1, MAGI-2,
MAGI-3/SLIPR

The MAGUK (Membrane Associated Guanylate kinase) family of proteins, whose prototypic member is PS95, is characterized by the presence of multi-PDZ and SH3 domains, and a single region of homology to Saccharomyces cerevisiae guanylate kinase (Guk) domain.¹

All MAGUK studied to date localize to regions of cell-cell contact, such as tight junctions in epithelial cells and synaptic junctions in neurons, and are believed to be involved in the assembly of multiprotein complexes via their protein-protein interaction domains. ² Using different screening systems, three novel closely related MAGUK protein were isolated: MAGI-1/BAP1, MAGI-2/rSCAM and MAGI-3/SLIPR. Similar to other MAGUK members, these three proteins have the characteristic multi-PDZ domains, and a guanylate kinase domain. However, WW domain replaces the characteristic SH3 domain present in other MAGUK proteins. Different components interacting with these proteins in a complex were identified. MAGI-1 was first identified in mouse, as a protein interacting with K-RasB.³ Three isoforms were identified and named MAGI-1a, MAGI-1b and MAGI-1c, of 1139, 1171 and 1374 amino acids, respectively. MAGI-2 was initially identified in rat, as a protein interacting with N-methyl-D-aspartate receptors (NMDA-R) and neuronal cell adhesion proteins, and was named S-SCAM.⁴ Three isoforms of S-SCAM were identified, of 1277, 1113 and 1053 amino acids length, respectively.⁵ MAGI-3 (also termed SLIPR) was identified in a two hybrid screening as a protein interacting with the tumor suppressor PTEN,⁶ and Receptor Tyrosine Phosphatase b (RPTPb).⁷ The overall homology among the MAGI proteins, especially regarding the structural domains, is high.

Sigma has developed anti peptide antibodies that specifically recognize MAGI-1, MAGI-2 and SLIPR/MAGI-3. They are carefully tested by immunoblotting, and are able to distinguish between the three proteins.

1. Anderson, J.M., Curr. Biol., 6, 382-384 (1996).
2. Fanning, A..S., and Anderson, J.M., Curr. Biol., 6, 1385-1388 (1996).
3. Dobrosostakaya, I., et al, J. Biol. Chem., 272, 31589-31597 (1997).
4. Hirao, K. et al., J. Biol. Chem., 273, 21105-21110 (1998).
5. Hirao, K. et al., J. Biol. Chem., 275, 2966-2972 (2000).
6. Wu, Y., et al., J. Biol. Chem., 275, 21477-21485 (2000).
7. Adamsky, K. et al., J. Cell Sci., In press (2003).