Expression of the aspartate/glutamate mitochondrial carriers aralar1 and citrin during development and in adult rat tissues.

Aralar1 and citrin are members of the subfamily of calcium-binding mitochondrial carriers and correspond to two isoforms of the mitochondrial aspartate/glutamate carrier (AGC). These proteins are activated by Ca2+ acting on the external side of the inner mitochondrial membrane. Although it is known that aralar1 is expressed mainly in skeletal muscle, heart and brain, whereas citrin is present in liver, kidney and heart, the precise tissue distribution of the two proteins in embryonic and adult tissues is largely unknown. We investigated the pattern of expression of aralar1 and citrin in murine embryonic and adult tissues at the mRNA and protein levels. In situ hybridization analysis indicates that both isoforms are expressed strongly in the branchial arches, dermomyotome, limb and tail buds at early embryonic stages. However, citrin was more abundant in the ectodermal components of these structures whereas aralarl had a predominantly mesenchymal localization. The strong expression of citrin in the liver was acquired postnatally, whereas the characteristic expression of aralar1 in skeletal muscle was detected at E18 and that in the heart began early in development (E11) and was preferentially localized to auricular myocardium in late embryonic stages. Aralar1 was also expressed in bone marrow, T-lymphocytes and macrophages, including Kupffer cells in the liver, indicating that this is the major AGC isoform present in the hematopoietic system. Both aralar1 and citrin were expressed in fetal gut and adult stomach, ovary, testis, and pancreas, but only aralar1 is enriched in lung and insulin-secreting beta cells. These results show that aralar1 is expressed in many more tissues than originally believed and is absent from hepatocytes, where citrin is the only AGC isoform present. This explains why citrin deficiency in humans (type II citrullinemia) only affects the liver and suggests that aralar1 may compensate for the lack of citrin in other tissues.

[1]  S. Scherer,et al.  Assignment1 of the SLC25A12 gene coding for the human calcium-binding mitochondrial solute carrier protein aralar to human chromosome 2q24 , 2000, Cytogenetic and Genome Research.

[2]  S. Scherer,et al.  Genomic structure of the adult-onset type II citrullinemia gene, SLC25A13, and cloning and expression of its mouse homologue. , 1999, Genomics.

[3]  A. Schoolwerth,et al.  Metabolite transport in mitochondria. , 1979, Annual review of biochemistry.

[4]  A. Moorman,et al.  Arginine-Metabolizing Enzymes in the Developing Rat Small Intestine , 1998, Pediatric Research.

[5]  J. Satrústegui,et al.  Molecular Cloning of Aralar, a New Member of the Mitochondrial Carrier Superfamily That Binds Calcium and Is Present in Human Muscle and Brain* , 1998, The Journal of Biological Chemistry.

[6]  E. Avner,et al.  Abundance of mRNAs encoding urea cycle enzymes in fetal and neonatal mouse liver. , 1989, Archives of biochemistry and biophysics.

[7]  F. Palmieri,et al.  The purified and reconstituted ornithine/citrulline carrier from rat liver mitochondria: electrical nature and coupling of the exchange reaction with H+ translocation. , 1997, The Biochemical journal.

[8]  J. Williamson,et al.  Interrelationships between gluconeogenesis and ureogenesis in isolated hepatocytes. , 1978, The Journal of biological chemistry.

[9]  T Dierks,et al.  Reaction mechanism of the reconstituted aspartate/glutamate carrier from bovine heart mitochondria. , 1988, Biochimica et biophysica acta.

[10]  J. Walker,et al.  Organization and sequence of the gene for the human mitochondrial dicarboxylate carrier: evolution of the carrier family. , 1999, The Biochemical journal.

[11]  T. Saheki,et al.  Citrin and aralar1 are Ca2+‐stimulated aspartate/glutamate transporters in mitochondria , 2001, The EMBO journal.

[12]  S. Scherer,et al.  Type II Citrullinemia (Citrin Deficiency): A Mysterious Disease caused by a Defect of Calcium-Binding Mitochondrial Carrier Protein , 2000 .

[13]  S. Scherer,et al.  The gene mutated in adult-onset type II citrullinaemia encodes a putative mitochondrial carrier protein , 1999, Nature Genetics.

[14]  T. Saheki,et al.  Role of argininosuccinate synthetase in the regulation of urea synthesis in the rat and argininosuccinate synthetase-associated metabolic disorder in man. , 1980, Advances in enzyme regulation.

[15]  J. Satrústegui,et al.  Characterization of a second member of the subfamily of calcium-binding mitochondrial carriers expressed in human non-excitable tissues. , 2000 .

[16]  P. Bovolenta,et al.  Expression pattern of cSix3, a member of the Six/sine oculis family of transcription factors , 1998, Mechanisms of Development.

[17]  J. Walker,et al.  Identification of the Human Mitochondrial Oxodicarboxylate Carrier , 2001, The Journal of Biological Chemistry.

[18]  T. Saheki,et al.  Pathogenesis of adult-onset type II citrullinemia caused by deficiency of citrin, a mitochondrial solute carrier protein: tissue and subcellular localization of citrin. , 2001, Advances in enzyme regulation.

[19]  V. Iacobazzi,et al.  The mitochondrial carnitine carrier protein: cDNA cloning, primary structure and comparison with other mitochondrial transport proteins. , 1997, The Biochemical journal.

[20]  J. M. Izquierdo,et al.  Control of the translational efficiency of beta-F1-ATPase mRNA depends on the regulation of a protein that binds the 3' untranslated region of the mRNA , 1997, Molecular and cellular biology.

[21]  P. Esbrit,et al.  Parathyroid hormone-related peptide stimulates DNA synthesis and insulin secretion in pancreatic islets. , 1999, The Journal of endocrinology.

[22]  S. Gordon,et al.  Macrophages in haemopoietic and other tissues of the developing mouse detected by the monoclonal antibody F4/80. , 1991, Development.

[23]  M. Runswick,et al.  The mitochondrial transport protein superfamily , 1993, Journal of bioenergetics and biomembranes.

[24]  A. Beaudet,et al.  A search for the primary abnormality in adult-onset type II citrullinemia. , 1993, American journal of human genetics.

[25]  J. Walker,et al.  The human mitochondrial deoxynucleotide carrier and its role in the toxicity of nucleoside antivirals , 2001, Proceedings of the National Academy of Sciences of the United States of America.