RESUMEN
The structure of Peptide T was determined by solution NMR spectroscopy, under strong structure-inducing conditions: 40% hexafluoro-2-propanol aqueous solution at 5 degrees C. Under these conditions it was possible to detect medium-range NOEs for the first time for this peptide. This allowed a much better-defined structure to be determined for Peptide T in comparison with earlier NMR and computational studies. Peptide structures consistent with the experimental restraints were generated using a restrained MD simulation with a full empirical force field. Residues 4-8 of Peptide T take on a well-defined structure with a heavy atom RMSD of 0.78 A. The structure is stabilized by hydrogen bonding to side-chain oxygen atoms of Thr 4 and Thr 8, as well as backbone hydrogen bonding between residues 5 and 7 that forms this region into a classic gamma-turn.
Asunto(s)
Péptido T/química , Propanoles/química , Estructura Terciaria de Proteína , Solventes/química , Secuencia de Aminoácidos , Frío , Humanos , Enlace de Hidrógeno , Modelos Moleculares , Simulación de Dinámica Molecular , Datos de Secuencia Molecular , Resonancia Magnética Nuclear Biomolecular , Péptido T/genéticaRESUMEN
Hyperplasia of vascular smooth muscle cells (VSMCs) occurs during HIV infection, part of a spectrum of HIV-mediated cardiovascular and microvascular pathologies. These changes are not due to direct viral infection but may involve the receptor-mediated action of viral proteins, such as the envelope protein gp120. We sought to identify gp120 receptors which might mediate the vascular smooth muscle cell hyperplasia present in HIV infection. A homology between neuropeptide Y (NPY) and the previously identified receptor-active V2-region of gp120 defined by an octapeptide sequence (Peptide T) related to VIP was noted. Since NPY is mitogenic for VSMCs we therefore determined whether gp120 shares this activity. Rat aortic VSMCs were treated for 24 h with human (h)NPY and gp120 in the presence of 0.5% serum to measure [3H]thymidine incorporation, an index of cell proliferation. NPY increased [3H]thymidine incorporation by 80% after a 24-h treatment in a bimodal fashion, with peak effects at 10(-10) M and 10(-8) M. Gp120 was an even more potent mitogen for VSMCs with peak activity occurring at 10(-12) M. Peptide T was equipotent with gp120, and slightly less efficacious, suggesting that this domain may mediate gp120 effects on VSMCs. When combined, gp120 and NPY acted to antagonize one another, lowering DNA synthesis to basal levels. The profile of pharmacologic inhibition supports a role for NPY receptors since antagonists of Y1 and Y2 subtypes substantially or completely inhibited gp120-mediated VSMC proliferation. This is the first demonstration of the proliferative effects of HIV viral protein gp120 on VSMCs. The effect appears to be mediated via gp120 sequences related to VIP, peptide T, and NPY. These ligands may be competitive inhibitors of binding or gp120 processing. Novel treatments may emerge based upon VIP and NPY receptor antagonists if further work substantiates a role for gp120 in the vascular abnormalities of AIDS.
Asunto(s)
Enfermedades Cardiovasculares/etiología , Proteína gp120 de Envoltorio del VIH/toxicidad , Infecciones por VIH/complicaciones , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/patología , Receptores de Neuropéptido Y/efectos de los fármacos , Receptores de Neuropéptido Y/fisiología , Secuencia de Aminoácidos , Animales , Enfermedades Cardiovasculares/patología , División Celular/efectos de los fármacos , Células Cultivadas , VIH/genética , VIH/patogenicidad , Proteína gp120 de Envoltorio del VIH/genética , Humanos , Hiperplasia , Mitógenos/farmacología , Datos de Secuencia Molecular , Neuropéptido Y/genética , Neuropéptido Y/farmacología , Neuropéptido Y/fisiología , Péptido T/genética , Péptido T/toxicidad , Ratas , Homología de Secuencia de Aminoácido , Péptido Intestinal Vasoactivo/genética , Péptido Intestinal Vasoactivo/farmacología , Péptido Intestinal Vasoactivo/fisiologíaRESUMEN
A bradykinin-potentiating peptide was isolated and characterized from venom of the scorpion Tityus serrulatus by chromatographic techniques followed by biological assays. The complete amino acid sequence (13 residues) of peptide is presented. The peptide potentiated the contractile activity of bradykinin on the isolated guinea-pig ileum, and inhibited the hydrolysis of bradykinin by angiotensin-converting enzyme from B. jararaca plasma and the conversion of angiotensin I to angiotensin II by kininase II from guinea-pig ileum tissue. The peptide also increased the depressor effect of bradykinin on arterial blood pressure in the anaesthetized rat.