Clara M. Szego

The lysosome as a mediator of hormone action.

Publisher Summary This chapter describes that nuclear invasion by lysosomal constituents serve as an obligatory early step in the coupling of metabolic responses leading to hormone-induced growth of specific target organs. Coordinated responses to events in the life of the whole cell involve the nucleus absolutely; both under conditions of rest and during circumstances leading to hormonally induced growth and differentiation. It has been found that participation of the phagolysosomal system in rapid and specific hormonal responses leads to invasion of the nucleoplasm by lysosomal components and to dramatic alterations of the cytoplasmic and intranuclear environments. Lysosomes have been shown to coalesce with the plasma membrane, a process that is reversible on interaction with a variety of chemical substances, which are preferentially accumulated in these organelles. Lysosomes also exhibit extraordinary intracellular mobility when their redistribution toward the nucleus is triggered by a variety of changes in the cellular environment. The target-specific lysosome, on activation by tropic hormone, serves as the mobile link for information transfer between the cell surface and the nucleoplasm.

Lysosomal functions in cellular activation: propagation of the actions of hormones and other effectors

Publisher Summary This chapter evaluates the aspects of the individual steps in the staging of vectorial pathway and assesses their potential metabolic consequences in the processing and execution of information delivered by agonist. The chapter determines from the analysis an array of effectors and target cells as possible, whether such a pattern is generalized or unique to only certain classes of effectors or target cells. The independent data and the implications of lysosomal function in propagation and coordination of transcellular events are also considered. The integration of information is derived from the analysis of interlocking problems that contributes to the understanding of critical molecular events associated with triggering of cellular responses to tropic hormones and other effectors.

Steroid hormone receptors in target cell membranes.

Numerous reports of rapid steroid hormone effects in diverse cell types cannot be explained by the generally prevailing theory that centers on the activity of hormone receptors located exclusively in the nucleus. Cell membrane forms of steroid hormone receptors coupled to intracellular signaling pathways may also play an important role in hormone action. Membrane-initiated signals appear to be the primary response of the target cell to steroid hormones and may be prerequisite to subsequent genomic activation. Recent dramatic advances in this area have intensified efforts to delineate the nature and biologic roles of all receptor molecules that function in steroid hormone-signaling pathways. This work has profound implications for our understanding of the physiology and pathophysiology of hormone actions in responsive cells and may lead to development of nvoel approaches for the treatment of many cell proliferative, metabolic, inflammatory, reproductive, cardiovascular, and neurologic defects.

Elevated serum cathepsin B1-like activity in women with neoplastic disease

Abstract Activities of selected hydrolytic enzymes were assessed in blind-coded sera of 121 women with invasive cancer of various organs. Acetylglucosaminidase, β-glucuronidase, and alkaline phosphatases were not markedly elevated above controls. In contrast, cathepsin B1-like (CB1) activity in sera before therapy averaged 45-fold greater than that of 56 normal controls ( P P P

Specific internalization of estrogen and binding to nuclear matrix in isolated uterine cells

Fractionation of rat uterine cells incubated at 22 degrees C with 0.2 nM [3H]-estradiol-17 beta (E2 beta) was performed to analyze the subcellular distribution of internalized hormone. The postnuclear supernatant of homogenates was resolved in Percoll density gradients into six major fractions defined by enzyme markers. Within 10 s, E2 beta concentrates at the density of plasma membranes and also at a more buoyant density (p = 1.052 +/- 0.001) with peak accumulation of hormone by 2 min. Thereafter, binding in the latter fraction declines concomitantly with appearance of a portion of hormone at higher densities corresponding to Golgi and lysosomes. E2 beta exhibits preferential accumulation in nuclear matrix from 5 to 60 min. Microfiltration and scanning electron microscopy of the buoyant 2-min peak fractions reveal organelles, 50-200 nm. These may represent endocytotic vesicles that serve as vehicles for nuclear transfer of hormone.

Lysosomal cathepsin B-like activity: mobilization in prereplicative and neoplastic epithelial cells

Extracellular release of acid thiol proteinase activity by prereplicative and neoplastic epithelial cells was studied in serum-free, chemically defined media (CDM) in vitro. Cells isolated from urinary bladder of male bullfrogs and endometrium of ovariectomized rats each showed preferential secretion of cathepsin B-like (CB) activity within 30 min after exposure to carcinogenic nitrosamines (5 X 10(-4) M) or to mitogenic estrogen 1 X 10(-9) M), respectively. In contrast, release of such proteinase, and stimulation of cell proliferation were far less extensive in rat preputial gland cells treated with estradiol-17 beta. Striking secretion of CB was characteristic of neoplastic, but not noncancerous, epithelial cells from human ectocervix. Neoplastic cells with divergent rates of cell-to-cell aggregation were separated by a filtration method. Those cells with high rates of intercellular aggregation also exhibited higher rates of cell proliferation in CDM, as well as in soft gels, and a greater level of CB release than corresponding cancer cells with a relatively low degree of intercellular adhesion. Brief treatment of neoplastic cervical epithelial cells with liposomes containing entrapped leupeptin, a potent inhibitor of CB activity, elicited a sharp reduction in both cellular thiol proteinase activity and cell growth as compared to appropriate controls. These data indicate that mobilization of lysosomal CB activity in prereplicative and malignant cells may play a significant role in the promotion of cell proliferation.

Lysosomal Membrane Stabilization and Antiestrogen Action in Specific Hormonal Target Cells (With colour plate I)

Recent advances in these laboratories in analysis of mechanisms of steroid hormone-induced growth have identified lysosomal function in the triggering of the coupled events leading from selective accu

Purification of estradiol receptor from rat uterus and blockade of its estrogen-binding function by specific antibody

Abstract Protein fractions which selectively bind 3H-estradiol-17β have been isolated from rat uterus by gel filtration and repeated ion-exchange chromatography. The purified preparation of major activity migrates essentially as a single component upon disc gel electrophoresis at pH 8.1 and 4.5, or on immunoelectrophoresis. Antireceptor γ-globulin selectively abolishes the estrogen-binding peak which characteristically sediments at “9.5 S ” on sucrose gradient centrifugation.

Differential effects of vasopressin on the water, calcium and lysosomal enzyme contents of mitochondria-rich and lysosome-rich (granular) epithelial cells isolated from bullfrog urinary bladder

Treatment of bullfrog urinary bladder with arginine vasopressin (AVP) elicited a dose-dependent increase in the basal movement of water and sodium across isolated tissues. Epithelial cells from the mucosal surface and incubated with 10 mU AVP/ml for 30 min retained a greater amount of intracellular water and calcium than cells not treated with hormone. The epithelial cells were further separated into two major fractions by density gradient centrifugation; cells damaged during these manipulations were separated from viable cells and discarded. Morphologcal examination of the two respective fractions indicated that they largely consisted of mitochondria-rich (MR) and granular (G) cell types which line the lumen of bullfrog bladder. The calcium content of MR cells averaged 25% greater than that of G-type cells. G cells had a markedly higher content of the characteristic lysosomal hydrolases, acid phsophatase and cathepsin B1, than that found in MR cells. Incubation of G cells with AVP elicited significant increments in water and calcium contents and extracellular release of lysosomal enzymes as compared to untreated cells. Among MR cells treated with AVP, cell calcium declines slightly but no significant increase in water content or extracellular hydrolase activity was detected in comparison with paired control cells. The physiological significance of acid proteinase release from G cells treated with AVP was evaluated in experiments with intact bladder. Proteinase inhibitors which suppress the activity of cathepsin B1 selectively antagonized the action of hormone on water permeation. The data suggest that alterations in the calcium and lysosomal hydrolase activity associated with G cells exposed to AVP may contribute to the hormone-induced water flow observed across the intact epithelium.

The influence of histamine and serotonin in promoting early uterine growth in the rat

Abstract Previous studies from these laboratories demonstrated that estrogen-induced histamine release, or histamine itself, may trigger the acute vasodilatation, hyperemia, and increase in capillary permeability which permit the accumulation of electrolytes, water and other metabolites in the stimulated target. These investigations have been extended to serotonin and heparin. Heparin was without effect 4 or 24 hr after intrauterine administration to adult ovariectomized rats. Serotonin, on the other hand, exhibited a striking similarity to histamine in its early influence on uterine vascularity and water imbibition, and was approximately 17 times as effective on a molar basis. Mitotic activity in the epithelium was conspicuous 24 hr after histamine treatment. Serotonin had a similar but less intense influence on epithelial mitoses. Intraluminally administered LSD-25 inhibited the hyperemia and water imbibition due to estrogen, even in adrenalectomized animals. Whether serotonin, which exhibits the estrogenicomimetic properties of histamine, normally functions in this capacity under circumstances associated with hormonal action remains to be determined.