ABSTRACT
One hundred and fifteen rats were ovariectomized, given daily injections of 10 microg of 17beta-estradiol 3-benzoate (EB), 250 microg of testosterone propionate (TP), or 10 microg of EB + 250 microg of TP in sesame oil (SO) or SO alone for 1, 1.5 and 2 mo, and heat shocked at 42 degrees C for 15 min. Immediately after heat shock, the increase in inducibly hyperphosphorylated heat shock transcription factor 1 (pHSF1) was highest in TP-treated and least in EB-treated rats. Heat shock transcription factor 1 (HSF1) also accumulated in the nuclei of neurons in TP-treated and exit the nuclei in EB-treated rats. While the subnuclear distribution of HSF1 was uniform and similar in control and heat-shocked EB-treated rats, it localized predominantly on euchromatin in heat-shocked TP-treated rats. An antibody, which preferentially recognized pHSF1, stained almost exclusively cell nuclei and demonstrated irregularly-shaped and round neuronal nuclei of heat-shocked TP- and EB-treated rats, respectively. Concomitantly, synthesis of the inducible heat shock protein Hsp70 was lowest in EB- and highest in TP-treated rats. In this model, testosterone prevents the heat shock-induced hyperphosphorylation of tau. Because HSF1 delays aging, its enhanced activation by testosterone strengthens the argument for a therapeutic role of androgens in Alzheimer's disease.
Subject(s)
Brain Chemistry/drug effects , DNA-Binding Proteins/metabolism , Estradiol/pharmacology , Heat-Shock Response/drug effects , Heat-Shock Response/genetics , Testosterone/pharmacology , Transcription Factors/metabolism , Animals , Blotting, Western , Body Weight/drug effects , Cell Nucleus/genetics , Cell Nucleus/metabolism , Cytoplasm/genetics , Cytoplasm/metabolism , DNA-Binding Proteins/genetics , Euchromatin/metabolism , Female , HSP70 Heat-Shock Proteins/biosynthesis , Heat Shock Transcription Factors , Hormone Replacement Therapy , Immunohistochemistry , Microscopy, Immunoelectron , Neurons/metabolism , Organ Size/drug effects , Ovariectomy , Phosphorylation , Rats , Rats, Sprague-Dawley , Thymus Gland/anatomy & histology , Thymus Gland/metabolism , Transcription Factors/geneticsABSTRACT
Mutations in the EGR2 gene cause a spectrum of Charcot-Marie-Tooth disease and related inherited peripheral neuropathies. We ascertained ten consecutive patients with various EGR2 mutations, report a novel de novo mutation, and provide longitudinal clinical data to characterize the natural history of the peripheral neuropathy. We confirmed that respiratory compromise and cranial nerve dysfunction are commonly associated with EGR2 mutations and can be useful in guiding molecular diagnosis. We also contrast morphological studies in the context of the I268N homozygous recessive mutation affecting the NAB repressor binding site and the R359W dominant-negative mutation in the zinc-finger domain.
Subject(s)
Early Growth Response Protein 2/genetics , Hereditary Sensory and Motor Neuropathy/genetics , Hereditary Sensory and Motor Neuropathy/pathology , Mutation , Amino Acid Sequence , Base Sequence , Binding Sites/genetics , Charcot-Marie-Tooth Disease/genetics , Charcot-Marie-Tooth Disease/pathology , Charcot-Marie-Tooth Disease/physiopathology , Child, Preschool , DNA/genetics , Early Growth Response Protein 2/chemistry , Genes, Dominant , Genes, Recessive , Hereditary Sensory and Motor Neuropathy/physiopathology , Homozygote , Humans , Infant , Infant, Newborn , Longitudinal Studies , Molecular Sequence Data , Mutation, Missense , Nerve Fibers, Myelinated/pathology , Nerve Fibers, Myelinated/physiology , Phenotype , Point Mutation , Sequence Homology, Amino Acid , Zinc Fingers/geneticsABSTRACT
We have shown previously that glycogen synthase kinase-3 beta (GSK-3 beta), cyclin-dependent kinase 5, and c-Jun NH(2)-terminal kinase become overactivated and hyperphosphorylate tau in heat-shocked female rats. This hyperphosphorylation of tau is estrogen-independent, prevented by androgens, and similar to Alzheimer's disease. In this study, ovariectomized (OVX) Sprague-Dawley rats (n = 75) received daily injections of 10 microg of 17 beta-estradiol benzoate (EB), or 250 microg of testosterone propionate (TP), or both EB and TP, or sesame oil (SO) vehicle for 4-6 weeks. In kinase assays of forebrain homogenates, overactivation of GSK-3 beta at 0-6 h after heat shock toward human recombinant tau, bovine tau, and phosphoglycogen synthase peptide 2 was prevented in OVX + TP and OVX + (EB + TP) but not in sham-OVX + SO, OVX + SO, and OVX + EB. Abs against inactive (pSer(9)) and activity-enhanced (pTyr(216)) GSK-3 beta showed marked increase of pSer(9)- and decrease of pTyr(216)-GSK-3 beta in both OVX + TP and OVX + (EB + TP) but not in sham-OVX + SO, OVX + SO, and OVX + EB. EB enhanced the overactivation of cyclin-dependent kinase 5. The activity of c-Jun NH(2)-terminal kinase was gonadal hormone-independent. The serum concentrations of testosterone and 17 beta-estradiol were 2.53 ng/ml and 201 pg/ml in OVX + TP and OVX + EB, respectively. These findings demonstrate that testosterone prevents the hyperphosphorylation of tau by inhibiting the heat shock-induced overactivation of GSK-3 beta and suggest that androgens given to aging men or, in combination with estrogens, to postmenopausal women could prevent or delay Alzheimer's disease.
