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1.
Acta Neuropathol ; 93(1): 43-9, 1997 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-9006656

RESUMEN

Prolactin (PRL)-producing pituitary adenomas are in some cases associated with deposition of abundant spherical amyloid; however, the origin of the amyloid has not been established. In this report, a PRL-producing pituitary adenoma composed almost entirely of spherical amyloid was analyzed biochemically. The tumor was removed surgically from a 56-year-old man. Immunohistochemical analysis revealed that residual tumor cells were strongly positive for PRL, while the spherical amyloid was not. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a band of approximately 4 kDa associated with the amyloid, which was not present in a nonamyloid producing prolactinoma. The 4-kDa band is similar in size to other known amyloidogenic peptides. Immunoblot analysis of the tumor material using polyclonal anti-human PRL antibodies revealed a small amount of normal-sized PRL; however, the abundant 4-kDa band was nonimmunoreactive. Amino acid sequencing showed that this peptide represents the first 34 amino acids of the intact PRL protein with a predicted size of 4313 Da. The presence of a small amount of normal-sized PRL in this tumor, as well as elevated circulating levels of PRL implies that intact PRL is being abnormally processed in the formation of spherical amyloid.


Asunto(s)
Amiloide/análisis , Neoplasias Hipofisarias/química , Prolactina/biosíntesis , Prolactinoma/química , Secuencia de Aminoácidos , Amiloide/ultraestructura , Electroforesis en Gel de Poliacrilamida , Humanos , Immunoblotting , Masculino , Persona de Mediana Edad , Datos de Secuencia Molecular , Neoplasias Hipofisarias/ultraestructura , Prolactinoma/ultraestructura
2.
J Neurochem ; 67(2): 845-56, 1996 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-8764615

RESUMEN

While studying the delivery of cytoplasmic proteins to the presynaptic terminals of CNS neurons, we discovered unique characteristics of one protein (p118) conveyed in slow component b (SCb) of axonal transport, the large group of proteins representing the cytoplasmic matrix. Alone among the SCb group, p118 coisolated with the synaptic junctional complex on biochemical fractionation of the radiolabeled synaptic regions. Purification and amino acid sequencing of this protein revealed it is most likely the guinea pig form of type I (brain) hexokinase (ATP:D-hexose 6-phosphotransferase, EC 2.7.1.1). Further biochemical treatments were consistent with this identity. The majority of type I brain hexokinase has been thought to be associated primarily with membranes, in particular the mitochondrial outer membrane. We found that the majority of type I hexokinase is transported toward the terminals at a rate at least 10 times slower than that exhibited by the maximal or average rate of mitochondria. This suggests that, in the axon, the enzyme exhibits transient or dynamic interactions with mitochondria that are moving more rapidly. It is not clear whether hexokinase binds exclusively to mitochondria, or also exhibits association with nonmitochondrial membranes. The unexpected enrichment of hexokinase during synaptic junctional complex purification may result from its strong association with the presynaptic membrane portion of the synapse.


Asunto(s)
Encéfalo/enzimología , Hexoquinasa/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Secuencia de Aminoácidos , Animales , Transporte Axonal , Bovinos , Compartimento Celular , Cobayas , Isoenzimas/metabolismo , Sustancias Macromoleculares , Masculino , Mitocondrias/enzimología , Datos de Secuencia Molecular , Ratas , Alineación de Secuencia , Homología de Secuencia de Aminoácido
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