title: Expression of the scaffolding PDZ protein glutaminase-interacting protein in mammalian brain.
abstract: A human brain cDNA clone coding for a novel PDZ-domain protein of 124 amino acids was previously isolated in our laboratory. The protein was termed glutaminase-interacting protein (GIP), because it interacts with the C-terminal region of the human L-type glutaminase (LGA). The pattern of expression and functions of GIP in brain are completely unknown, so its significance remains undefined. Here we describe the expression of GIP mRNA and protein in mammalian brain. Northern blot analysis revealed that GIP mRNA was ubiquitous in most regions of human brain but was particularly abundant in spinal cord. The presence of the protein in rat and monkey brain was studied at the regional, cellular, and subcellular level by immunocytochemistry. The protein was found to be present in both neurons and astrocytes, with a cytosolic and mitochondrial subcellular localization. Double immunofluorescence labeling with anti-GIP and anti-LGA antibodies using confocal microscopy revealed colocalization of both proteins in astrocyte cell processes and their perivascular end feet. Electron microscopy of rat brain neurons revealed GIP immunoreactivity concentrated also in the nuclear envelope and the plasma membrane. The multiple locations for GIP in mammalian brain are in agreement with known protein interaction partners reported for this PDZ protein. The findings presented here support a role of GIP as an important scaffold in both astrocytes and neurons and point toward astrocytic processes and perivascular end feet as plausible anatomical substrates for interaction with glutaminase.
authors.affiliation: Departamento de Biología Molecular y Bioquímica, Universidad de Málaga, Málaga, Spain.
authors.forename: Lucía
authors.initials: L
authors.lastname: Olalla
authors.forename: Antonia
authors.initials: A
authors.lastname: Gutiérrez
authors.forename: Antonio J
authors.initials: AJ
authors.lastname: Jiménez
authors.forename: Juan F
authors.initials: JF
authors.lastname: López-Téllez
authors.forename: Zafar U
authors.initials: ZU
authors.lastname: Khan
authors.forename: Juan
authors.initials: J
authors.lastname: Pérez
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Alonso
authors.forename: Vanessa
authors.initials: V
authors.lastname: de la Rosa
authors.forename: José A
authors.initials: JA
authors.lastname: Campos-Sandoval
authors.forename: Juan A
authors.initials: JA
authors.lastname: Segura
authors.forename: J Carlos
authors.initials: JC
authors.lastname: Aledo
authors.forename: Javier
authors.initials: J
authors.lastname: Márquez
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D015152:Blotting, Northern; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism*; D015870:Gene Expression; D005972:Glutaminase / Q000096:biosynthesis*; D000882:Haplorhini; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D018613:Microscopy, Confocal; D016253:Microscopy, Immunoelectron; D009474:Neurons / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D013116:Spinal Cord / Q000378:metabolism
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D012333:RNA, Messenger; C421249:TAX1BP3 protein, human; D005972:Glutaminase