Effect of specific inhibition of gamma-glutamyl transpeptidase on amino acid uptake by mammary gland of the lactating rat

AbstractWe showed [Biochem. J. (1981) 194, 99–102] that inhibition of γ-glutamyl transpeptidase in vivo with serine-borate decreases amino acid uptake by mammary gland. However, doubts arose about the validity of this inhibitor in metabolic studies because it must be used in very large amounts. New Inhibitors have been isolated, like anthglutin and acivicin, which are effective at low concentrations in vivo. Here, we show that treatment of lactating rats with these substances decreases the transpeptidase activity and the amino acid uptake by the gland. These results support the hypothesis that the γ-glutamyl cycle functions as an amino acid transport system in mammary gland

Calpains, the proteases of two faces controlling the epithelial homeostasis in mammary gland

Calpain-1 and calpain-2 are calcium-dependent Cys-proteases ubiquitously expressed in mammalian tissues with a processive, rather than degradative activity. They are crucial for physiological mammary gland homeostasis as well as for breast cancer progression. A growing number of evidences indicate that their pleiotropic functions depend on the cell type, tissue and biological context where they are expressed or dysregulated. This review considers these standpoints to cover the paradoxical role of calpain-1 and -2 in the mammary tissue either, under the physiological conditions of the postlactational mammary gland regression or the pathological context of breast cancer. The role of both calpains will be examined and discussed in both conditions, followed by a brief snapshot on the present and future challenges for calpains, the two-gateway proteases towards tissue homeostasis or tumor development

Synergism between the Two Membranes of the Blood-brain Barrier: Glucose and Amino Acid Transport

Brain capillary endothelial cells, which are connected by extensive tight junctions and are polarized into luminal (blood-facing) and abluminal (brain-facing) plasma membrane domains, form the blood-brain barrier (BBB). The polar distribution of transport proteins mediates glucose and amino acid (AA) homeostasis in the brain. The ability to isolate the luminal and abluminal membranes has permitted the study of each side of the BBB separately in vitro and yielded new information on BBB function. The two membranes have different characteristics. Facilitative transporters were found on both membranes in a position to permit the bidirectional transport of glucose, almost all amino acids and taurine. Na+-dependent transporters were only found on abluminal membranes. The Na+-dependent transporters on the abluminal side are capable of removing virtually all amino acids including acidic AA from the extracellular fluid of brain (ECF). The presence of Na+-dependent carriers on the abluminal membrane provides a mechanism by which the concentrations of AA, glucose and taurine in the ECF of brain may be maintained at optimal levels under physiological and pathophysiological circumstances. Facilitative carriers for glutamine (n) and glutamate (xg-) are found only in the luminal membrane of the BBB. This organization allows the net removal of acidic and nitrogen-rich AA from brain, and explains the low rate of glutamate and glutamine penetration into the central nervous system. The presence of a g-glutamyl cycle at the luminal membrane and Na+-dependent AA transporters at the abluminal membrane may serve to modulate movement of AA from blood to brain. The g-glutamyl cycle is expected to generate pyroglutamate within the endothelial cells. Pyroglutamate stimulates Na+-dependent AA transporters at the abluminal membrane thereby reducing net influx of AA the to brain. It is now clear the BBB may actively participate in the regulation of the AA content of the brain as well as contributing to the control of brain osmolarity

Activación de las calpaínas en la glándula mamaria tras el destete: identificación mediante Proteómica de nuevas dianas

Comunicaciones a congreso

Id2 leaves the chromatin of the E2F4-p130-controlled c-myc promoter during hepatocyte priming for liver regeneration

The Id (inhibitor of DNA binding or inhibitor of differentiation) helix-loop-helix proteins are involved in the regulation of cell growth, differentiation and cancer. The fact that the molecular mechanisms of liver regeneration are not completely understood prompted us to study the fate of Id2 in proliferating liver. Id2 increases in liver regeneration after partial hepatectomy, following the early induction of its gene. Co-immunoprecipitation shows that Id2 forms a complex with E2F4, p130 and mSin3A in quiescent liver and all these components are present at the c-myc promoter as shown using ChIP (chromatin immunoprecipitation). Activation of c-myc during hepatocyte priming (G0-G1 transition) correlates with the dissociation of Id2 and HDAC (histone deacetylase), albeit p130 remains bound at least until 6 h. Moreover, as the G0-G1 transition progresses, Id2 and HDAC again bind the c-myc promoter concomitantly with the repression of this gene. The time course of c-myc binding to the Id2 promoter, as determined by ChIP assays is compatible with a role of the oncoprotein as a transcriptional inducer of Id2 in liver regeneration. Immunohistochemical analysis shows that Id2 also increases in proliferating hepatocytes after bile duct ligation. In this case, the pattern of Id2 presence in the c-myc promoter parallels that found in regenerating liver. Our results may suggest a control role for Id2 in hepatocyte priming, through a p130 dissociation-independent regulation of c-my

Cationic amino acid transport across the blood-brain barrier is mediated exclusively by system y+

Cationic amino acid (CAA) transport is brought about by two families of proteins that are found in various tissues: Cat (CAA transporter), referred to as system y+, and Bat [broad-scope amino acid (AA) transporter], which comprises systems b0,+, B0,+, and y+L. CAA traverse the blood-brain barrier (BBB), but experiments done in vivo have only been able to examine the BBB from the luminal (blood-facing) side. In the present study, plasma membranes isolated from bovine brain microvessels were used to identify and characterize the CAA transporter(s) on both sides of the BBB. From these studies, it was concluded that system y+ was the only transporter present, with a prevalence of activity on the abluminal membrane. System y+ was voltage dependent and had a Km of 470 ± 106 μM (SE) for lysine, a Ki of 34 μM for arginine, and a Ki of 290 μM for ornithine. In the presence of Na+, system y+ was inhibited by several essential neutral AAs. The Ki values were 3–10 times the plasma concentrations, suggesting that system y+ was not as important a point of access for these AAs as system L1. Several small nonessential AAs (serine, glutamine, alanine,and glycine) inhibited system y+ with Ki values similar to their plasma concentrations, suggesting that system y+ may account for the permeability of the BBB to these AAs. System y+ may be important in the provision of arginine for NO synthesis. Real-time PCR and Western blotting techniques established the presence of the three known nitric oxide synthases in cerebral endothelial cells: NOS-1 (neuronal), NOS-2 (inducible), and NOS-3 (endothelial). These results confirm that system y+ is the only CAA transporter in the BBB and suggest that NO can be produced in brain endothelial cells

Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences

The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & Nemésio 2007; Donegan 2008, 2009; Nemésio 2009a–b; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on 18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based researchers who signed it in the short time span from 20 September to 6 October 2016