Prolyl carboxypeptidase regulates energy expenditure and the thyroid axis.

Hypothalamic α-melanocyte-stimulating hormone (α-MSH) plays a central role in regulating energy uptake and expenditure. Prolyl carboxypeptidase (PRCP), a protease expressed in the hypothalamus, is responsible for the degradation of α-MSH. PRCP null animals (PRCP(gt/gt) mice) display elevated α-MSH in the hypothalamus, lower body weight, and are protected from diet induced obesity. Here, we report that PRCP(gt/gt) mice have a significant decrease in fat mass, although an increase in lean mass was also observed. In agreement with low fat accumulation, reduced leptin levels were found. Consistent with the effect of α-MSH on energy metabolism, PRCP(gt/gt) mice had increased energy expenditure with elevated circulating thyroid hormone levels and brown adipose tissue uncoupling protein 1 mRNA levels compared with control mice when exposed to regular diet. TRH mRNA levels in the PVN were significantly higher in fed PRCP(gt/gt) animals compared with fed wild-type controls. Fasting significantly decreased TRH mRNA levels in both PRCP(gt/gt) and wild-type (WT) mice. However, TRH mRNA levels in fasted PRCP(gt/gt) animals were significantly higher than those of fasted WT mice. Refeeding analysis after fasting showed a reduced food intake in PRCP(gt/gt) compared with WT mice. Finally, TRH mRNA levels in T(3)-treated hypothyroid PRCP(gt/gt) mice showed a non significant reduction compared with those of hypothyroid PRCP(gt/gt) mice, supporting the impairment of the hypothalamo-pituitary-thyroid axis in PRCP(gt/gt) mice. All together, these data confirm that PRCP plays a role in the regulation of energy metabolism.

Identification and assessment of the role of a nominal phospholipid binding region of ORP1S (oxysterol-binding-protein-related protein 1 short) in the regulation of vesicular transport.

The ORPs (oxysterol-binding-protein-related proteins) constitute an enigmatic family of intracellular lipid receptors that are related through a shared lipid binding domain. Emerging evidence suggests that ORPs relate lipid metabolism to membrane transport. Current data imply that the yeast ORP Kes1p is a negative regulator of Golgi-derived vesicular transport mediated by the essential phosphatidylinositol/phosphatidylcholine transfer protein Sec14p. Inactivation of Kes1p function allows restoration of growth and vesicular transport in cells lacking Sec14p function, and Kes1p function in this regard can be complemented by human ORP1S (ORP1 short). Recent studies have determined that Kes1p and ORP1S both bind phospholipids as ligands. To explore the function of distinct linear segments of ORP1S in phospholipid binding and vesicular transport regulation, we generated a series of 15 open reading frames coding for diagnostic regions within ORP1S. Purified versions of these ORP1S deletion proteins were characterized in vitro, and allowed the identification of a nominal phospholipid binding region. The in vitro analysis was interpreted in the context of in vivo growth and vesicle transport assays for members of the ORP1S deletion set. The results determined that the phospholipid binding domain per se was insufficient for inhibition of vesicular transport by ORP1S, and that transport of carboxypeptidase Y and invertase from the Golgi may be regulated differentially by specific regions of ORP1S/Kes1p.

Estudo da regulação da expressão do gene da carboxipeptidase M de camundongo / Expression regulation studies of the carboxypeptidase M gene in mouse

A caracterização da estrutura molecular da carboxipeptidase M humana originou os estudos da enzima em camundongos. Utilizando análise computacional a estrutura do gene em camundongos foi determinada comparando a seqüência de humanos no banco de dados genômico de camundongos. As duas seqüências apresentaram 82 por cento de similaridade entre elas. Foram determinados todos os fatores envolvidos na caracterização do RNAm como tamanho de exons e introns, região de catálise, região hidrofóbica, peptídeo sinal, sítios de glicosilação e glutâmicos catalíticos. A análise computacional proporcionou também a observação de um EST o qual também se tomou objeto de estudos. Após serem definidos todos os fatores pertencentes ao gene iniciamos os experimentos com a demonstração da atividade luciferase para os promotores da CPM e do EST. A análise foi feita em três diferentes tipos celulares para evidenciar a existência de atividade promotora e sua diferente regulação nessas linhagens. O EST foi clonado e transfectado em células para dosagem fluorimetrica de sua atividade carboxipeptidase básica. A técnica de PCR em tempo real foi utilizada para obtenção dos resultados de expressão gênica relativa tanto da carboxipeptidase M como do EST em camundongos nas fases embrionária, neonatal e adulta. Com base nos dados obtidos pudemos concluir a estrutura da carboxipeptidase M e do EST encontrado, sua regulação transcricional e padrão de expressão nos diversos RNAs extraídos de tecidos de camundongos.

Zinc binding in proteins and solution: a simple but accurate nonbonded representation.

Force field parameters that use a combination of Lennard-Jones and electrostatic interactions are developed for divalent zinc and tested in solution and protein simulations. It is shown that the parameter set gives free energies of solution in good agreement with experiment. Molecular dynamics simulations of carboxypeptidase A and carbonic anhydrase are performed with these zinc parameters and the CHARMM 22 beta all-atom parameter set. The structural results are as accurate as those obtained in published simulations that use specifically bonded models for the zinc ion and the AMBER force field. The inclusion of longer-range electrostatic interactions by use of the Extended Electrostatics model is found to improve the equilibrium conformation of the active site It is concluded that the present parameter set, which permits different coordination geometries and ligand exchange for the zinc ion, can be employed effectively for both solution and protein simulations of zinc-containing systems.

Phenylalanine-to-tyrosine singlet energy transfer in the archaebacterial histone-like protein HTa.

The Archaebacterium Thermoplasma acidophilum has a histone-like protein (HTa) abundantly associated with its deoxyribonucleic acid. Each native tetrameric complex of HTa contains 20 phenylalanine residues, 4 tyrosine residues, and no tryptophan. When the protein was excited by radiation at 252 nm, which is a wavelength absorbed predominantly by phenylalanine, the fluorescent emission was mostly from tyrosine. According to the excitation spectrum for this tyrosine fluorescence, the cause was energy transfer from phenylalanine, which occurred with about 50% efficiency. When the tyrosine residues were removed enzymatically, the excited-state lifetime of the phenylalanine residues nearly doubled. Because of energy transfer, the tyrosine emission had two apparent fluorescence decay lifetimes; one lifetime (3.9 ns) was that of tyrosine while the second (12.1 ns) corresponded to the excited state of phenylalanine.

A histone-like protein (HTa) from Thermoplasma acidophilum. I. Purification and properties.

A histone-like protein (HTa) has been isolated from cell extracts of Thermoplasma acidophilum by column chromatography on DNA-cellulose, hydroxylapatite, and Sephadex G-75, HTa elutes from DNA-cellulose in two fractions, one of which contains an 80-residue form of the protein with an NH2-terminal sequence of Val-Gly. The other fraction apparently contains the 89-residue species, in addition to a 90-residue form of the protein with the NH2-terminal sequence Met-Val. The sequence of 47 residues from the NH2 terminus of the 89-residue protein was established by automated Edman degradation. HTa is characterized by the following properties: 22% of its residues are lysine and arginine; the lysine:arginine ratio is 2.33; the absorption spectrum of the protein is distinctive due to the lack of tryptophan and the presence of 1 tyrosine and 5 phenylalanine residues; and the protein stabilizes DNA against thermal denaturation (Stein, D. B., and Searcy, D. G. (1978) Science 202, 219-221) and condenses DNA into spherical particles. All of these characteristics indicate that HTa resembles eukaryotic histones, but there are distinctive differences.