Endocytosis of Peptide Hormones and Other Ligands

Posner, Barry I.; Khan, Masood N.; Bergeron, John J.M.

doi:10.1210/edrv-3-3-280

Cited by 91 publications

(29 citation statements)

References 156 publications

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“…Similar observations made in other endocytic epithelial cells (Miller, 1960;Ericsson, 1964;Miller and Palade, 1964;Maunsbach, 1966a,b;Neustein and Maunsbach, 1966;Ericsson and Trump, 1969;van Deurs, 1978a,b;van Deurs and Nilausen, 1982;Morales and Hermo, 1984) have been taken to suggest a progressive transformation of the dilated vacuoles into secondary lysosomes. It cannot be excluded, however, that small vesicles serve as carriers of tracers from one compartment to another (Posner et al, 1982). In the present work, the transformation of multivesicular bodies into dense lysosomes is suggested by their sequential disappearance from the supranuclear region of the noncihated epithelial cells following ligature of the proximal part of the ductuli efferentes (Figs.…”

Section: Discussionmentioning

confidence: 57%

“…Recent studies on the endocytic process have identified several types of endocytosis, i.e., fluid-phase, adsorptive, and receptor-mediated endocytosis (Silverstein et al, 1977;Posner et al, 1982;Steinman et al, 1983). While adsorptive endocytosis involves the binding of particles or molecules to nonspecific binding sites of the cell membrane, fluidphase endocytosis refers to a nonselective uptake of material by the cell.…”

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confidence: 99%

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Endocytosis in nonciliated epithelial cells of the ductuli efferentes in the rat

1984

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The nonciliated cells lining the ductuli efferentes presented three distinct cytoplasmic regions. The apical region contained, in addition to cisternae of endoplasmic reticulum and mitochondria, two distinct membranous elements. The tubulovesicular system consisted of dilated tubules connected to the apical plasma membrane and subjacent distended vesicular profiles. The apical tubules, not connected to the cell surface, consisted of numerous densely stained tubules of small size which contain a compact, finely granulated material. The supranuclear region, in addition to a Golgi apparatus and ER cisternae, contained dilated vacuoles, pale and dense multivesicular bodies, as well as numerous dense granules identified cytochemically as lysosomes. The basal region contained the nucleus and many lipid droplets. The endocytic activity of these cells was investigated using cationic ferritin (CF) and concanavalin-A-ferritin (Con-A-ferritin) as markers of adsorptive endocytosis; and native ferritin (NF), concanavalin-A-ferritin in the presence of alpha-methyl mannoside, and horseradish peroxidase or albumin bound to colloidal gold for demonstrating fluid-phase endocytosis. These tracers were injected separately into the rete testis, and animals were sacrificed at various time intervals after injection. At 1 min, CF or Con-A-ferritin were seen bound to the apical plasma membrane, to the membrane of microvilli, and to the membrane delimiting elements of the tubulovesicular system. Between 2 and 5 min, these tracers accumulated in the densely stained apical tubules and at 15 min in the dilated vacuoles. Between 30 min and 1 hr, the tracers appeared in multivesicular bodies of progressively increasing density, whereas at 2 hr and later time intervals, many dense lysosomal elements became labeled. The tracers for fluid-phase endocytosis showed a distribution similar to that for CF or Con-A-ferritin except that they did not bind to the apical plasma membrane, microvilli, or membrane delimiting the tubulovesicular system. At no time interval were any of the tracers observed in the abluminal spaces. Thus, the nonciliated epithelial cells of the ductuli efferentes are actively involved in fluid-phase and adsorptive endocytosis, both of which result in the sequestration of endocytosed material within the lysosomal apparatus of the cell.

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Section: Discussionmentioning

confidence: 57%

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confidence: 99%

Endocytosis in nonciliated epithelial cells of the ductuli efferentes in the rat

1984

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“…(ii) These findings demonstrate that the response of larvae to inducing molecules can be modulated by alterations in the number of functional receptors for the molecules. This mechanism of regulation, which is known to occur in a variety of other receptor-mediated responses to amino acids (33,34), neurotransmitters (35,36), hormones (37,38), and growth factors (39), is thus shown to be also operative in a chemosensory system that controls behavior and development in response to environmental signals.…”

Section: Discussionmentioning

confidence: 99%

Availability of chemosensory receptors is down-regulated by habituation of larvae to a morphogenetic signal.

Trapido-Rosenthal¹,

Morse²

1986

Proc. Natl. Acad. Sci. U.S.A.

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Larvae of the gastropod mollusc Haliotis rufescens are induced to settle from the plankton and metamorphose in response to exogenous y-aminobutyric acid (GABA) and a number of GABA-mimetic compounds, including a GABA-mimetic inducer uniquely associated with the surfaces of the naturally recruiting algae. Previous evidence has shown that recognition of these inducers is mediated by specialized chemosensory receptors on the larval epithelium and that transduction of the morphogenetic signal then is mediated by cAMP and excitatory depolarization. We demonstrate here the specific and saturable labeling of a population of larval receptors with the GABA analog f-(p-chlorophenyl)-[3H]GABA ([3H]baclofen); identification of these labeled receptors with those controlling metamorphosis is suggested by four independent criteria: (i) the effectiveness of GABA and its close structural analogs to induce metamorphosis is closely correlated with the effectiveness ofthese compounds to compete for binding to this receptor; (ii) the natural inducer purified from the recruiting algae competes for binding to this receptor; (iii) (-)-[3H]baclofen specifically bound to the receptors is shed from the larvae after %20 hr, at the time corresponding to the metamorphic abscission and shedding of sensory cilia and other structures from the larvae; and (iv) the availability of the receptors for labeling and the ability of the larvae to respond to GABA and GABA analogs can be down-regulated in parallel by habituation of the larvae early in their development. These down-regulated larvae are fully capable of settlement and metamorphosis in response to agents that elevate intracellular cAMP or depolarize the chemosensory membrane, confirming that down-regulation is confined to the receptors, with no effect on the postreceptor pathway. The results reported here thus suggest that the sensitivity of marine invertebrate larvae to morphogenetic stimuli from the environment can be downregulated by reduction in the number of chemosensory receptors available for interaction with the molecules that induce settlement and metamorphosis. In this respect, chemosensory receptors for environmental and morphogenetic signals are demonstrated biochemically to respond to habituation in a similar manner to neuronal and hormonal receptors.Larvae of many benthic marine invertebrate animals, after dispersal in the plankton, are induced to settle and metamorphose only upon recognition of specific substrata (1-8). Larvae (0.2 mm) of the Pacific red abalone, Haliotis rufescens, a gastropod mollusc, are induced to settle, attach to substrata, and metamorphose by chemosensory recognition of y-aminobutyric acid (GABA)-mimetic molecules that are uniquely associated with the surfaces of crustose red algae (9, 10). These purified natural inducers alone, GABA, and a number of GABA analogs are sufficient to induce this genetically programed behavioral and morphogenetic sequence (11-14); in the absence of such inducers, the larvae do not settle or metamorphose (11)(12)(13)...

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“…Although other possi bilities remain viable, our findings appear to be most con sistent with a model of LHRH action which involves intra cellular localization of the hormone itself. This issue of a priori internalization preceding function is highly contro versial and is currently under intensive investigation for many peptide hormone systems [20], Within recent years, evidence has been forthcoming that LHRH enters anterior pituitary cells as an intact molecule, and can then be found within or attached to intracellular organelles [4]. Such ob servations have led to speculated correlations between such intracellular interactions and the release and/or synthesis of LH [13].…”

Section: Discussionmentioning

confidence: 99%

Specific, Estrogen-Sensitive Alterations in Anterior Pituitary Cytoplasmic and Nuclear Estrogen Receptors Actuated by LHRH

Singh¹,

Muldoon²

1983

Neuroendocrinology

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We have previously demonstrated that LHRH is capable of eliciting a dramatic and direct elevation of anterior pituitary levels of nuclear estrogen receptors (E2R) [18, 24]. This action was manifest under both in vitro and in vivo conditions, and could not be attributed to an amplification of the rate or extent of cytosol E2R binding, activation or transloca-tion. In view of the implications of these observations in terms of estrogen-LHRH interplay in regulation of gonadotropin secretion, we have further explored the nature, specificity and estrogen dependency of the LHRH effect. TRH, a long-acting agonist, (D-Ala⁶, des-Gly¹⁰)LHRH-N-ethylamide (LHRH-A), and an antagonist, N-Ac-D-p-Cl-Phe¹², D-Trp³, D-Phe⁶, D-Ala¹⁰-LHRH (LHRH-ANT), were compared with LHRH for their ability to alter compartmental E2R concentrations following incubation in vitro. Either intact dispersed anterior pituitary cells or isolated cytosol and nuclei from pituitary homogenates were used as receptor source. LHRH-A and LHRH both caused a 40–60% decrease in the cytoplasmic E2R binding capacity of intact cells following incubation of 30 min at 37 °C; the magnitude of the inhibition was dose independent over a peptide range of 0.1–1000 pmol/pituitary. In contrast, TRH caused a dose-related decrease in cytosol E2R binding. When nuclear E2R levels were assessed, significant dose dependent increases were observed with both LHRH and LHRH-A treatment. The effective dose of LHRH-A was approximately an order of magnitude lower than that of LHRH. TRH, on the other hand, over a wide concentration range (0.3–3,000 pmol/pituitary), had no significant effect on specific nuclear estrogen binding. In isolated nuclei, as in the intact cell studies, LHRH and LHRH-A were stimulatory, while TRH effected no alteration of E2R binding levels. The LHRH effect could be totally blocked by LHRH-ANT. In isolated cytosol, TRH did not affect E2R binding, whereas LHRH and LHRH-A were both mildly stimulatory. The effectiveness of LHRH in enhancing nuclear E2R binding correlated directly with the endogenous estrogen titers of the animals. In tissue from ovariectomized animals primed with 0.1 μg estradiol/day, LHRH was 4 times more potent as a stimulator of nuclear E2R than in tissue from nonprimed castrate animals. If the priming dose was increased to 1.0 μg/day, a further significant increase in sensitivity of nuclear E2R to LHRH was observed over the 0.1 μg priming dose level. The results of these studies attest to the releasing hormone specificity of changes in anterior pituitary E2R levels, and to the involvement of estrogen-LHRH sensitization in this process, analogous to the well-documented estrogen-LHRH interplay in regulation of LHRH release.

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Endocytosis of Peptide Hormones and Other Ligands

Cited by 91 publications

References 156 publications

Endocytosis in nonciliated epithelial cells of the ductuli efferentes in the rat

Endocytosis in nonciliated epithelial cells of the ductuli efferentes in the rat

Availability of chemosensory receptors is down-regulated by habituation of larvae to a morphogenetic signal.

Specific, Estrogen-Sensitive Alterations in Anterior Pituitary Cytoplasmic and Nuclear Estrogen Receptors Actuated by LHRH

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