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(Греч.: ένδον - внутри, κρίνω - отделять + λόγος - учение; положение; 1913).
Рецепторы могут быть расположены на наружной поверхности мембран клетки (рецепторы мембран) или в цитоплазме. Вещества, комбинирующиеся с рецепторами, служат средством передачи информации. Содержание этой информации может быть различным: информация о цели, управляющая информация, информация о среде, информация о состоянии объекта управления, информация о результатах управления. В числе переносчиков информации могут быть нейромедиаторы, гормоны, иммуноглобулины и другие вещества. Образующийся комплекс «вещество-рецептор» может непосредственно или через цепь посредников специфически влиять на интенсивность тех или иных процессов метаболизма клетки.
Эндокринология - это область знаний, процесс познания, практические знания об эндокринной системе. Как область знаний эндокринология является разделом физиологии. Как процесс познания эндокринология представляет собой исследование эндокринной системы. Как практические знания эндокринология предназначена для морально оправданного использования научных знаний об организации отношений вероятностных сущностей и явлений эндокринной системы на практике для управления этими сущностями и явлениями в норме и при патологии.
Типичной начальной целью пептидных гормонов являются цитоплазматические рецепторы, передающие информацию к цитоплазматическим структурам. Вместе с тем ясно, что эти рецепторы могут воспринимать информацию, предназначенную для управления транскрипционной активностью ядра клетки. Такое средство управления реализуется с участием ферментов цитоплазмы (например, киназ и фосфатаз). В свою очередь цитоплазматические ферменты взаимодействуют с конечной целью - транскрипционными факторами, непосредственно управляющими экспрессией определённых генов.
Таблица. Биохимические рецепторы плазалемм и их эффекторы. Пути сигналов. I. По-русски (In Russian) = G Protein–Coupled Seven-Transmembrane (GPCR) • β-Adrenergic
Gsα, adenylate cyclase Stimulation of cyclic AMP production, protein kinase A • PTH, PTHrP
Ca2+ channels Calmodulin, Ca2+-dependent kinases • β-Adrenergic
Giα • Inhibition of cyclic AMP production
TRH, GnRH Gq, G11 Phospholipase C, diacylglycerol, IP3, protein kinase C,
voltage-dependent Ca2+ channels II. По-русски (In Russian) = Receptor Tyrosine Kinase Insulin, IGF-I Tyrosine kinases, IRS MAP kinases, PI 3-kinase; AKT, also known as protein kinase B, PKB EGF, NGF Tyrosine kinases, ras Raf, MAP kinases, RSK III. По-русски (In Russian) = Cytokine Receptor–Linked Kinase GH, PRL JAK, tyrosine kinases STAT, MAP kinase, PI 3-kinase, IRS-1 IV. По-русски (In Russian) = Serine Kinase Activin, TGF-β, MIS Serine kinase Smads
Обозначения:
ACTH, adrenocorticotrophic hormone;
MAP, mitogen-activated protein;
Схема. Сигналы, воспринимаемые биохимическими рецепторами плазмалеммы.
Примечание: Membrane receptor signaling.
Схема. Гормональная передача управляющих сигналов биохимическим рецепторам плазмалеммы клетки-мишени и внутриклеточным рецепторам = Hormonal signaling by cell surface and intracellular receptors.
Примечание: Figure 1-2 Hormonal signaling by cell surface and intracellular
receptors. The receptors for the water-soluble polypeptide
hormones, luteinizing hormone (LH), and insulin-like
growth factor 1 (IGF-1), are integral membrane proteins
located at the cell surface. They bind the hormone-utilizing
extracellular sequences and transduce a signal through the
generation of second messengers: cyclic adenosine monophosphate
(cAMP) for the LH receptor and tyrosinephosphorylated
substrates for the IGF-1 receptor. Although
effects on gene expression are indicated, direct effects on
cellular proteins (e.g., ion channels) are also observed. In
contrast, the receptor for the lipophilic steroid hormone,
progesterone, resides in the cell nucleus. It binds the
hormone and becomes activated and capable of directly
modulating target gene transcription.) AC, Adenylate cyclase;
G, heterotrimeric G protein; mRNAs, messenger RNAs;
PKA, protein kinase A; R, receptor molecule; TF, transcription
factor; Tyr, tyrosine found in protein X; X, unknown protein
substrate. (Reproduced from Mayo K. Receptors: molecular
mediators of hormone action. In: Conn PM, Melmed S, eds.
Endocrinology: Basic and Clinical Principles. Totowa, NJ: Humana
Press, 1997:11.)
Схема. Рецептор тирозинкиназ = Receptor tyrosine kinases.
Примечание: Figure 5-1 Receptor tyrosine kinases. Three of the 16 families of receptor tyrosine kinases are diagrammed.2,3 All receptor tyrosine kinases possess an
extracellular domain containing the ligand-binding site, a single transmembrane domain, and an intracellular portion containing the tyrosine kinase domain.
Several structural motifs (i.e., cysteine-rich domain, immunoglobulin (Ig)-like domain, tyrosine kinase domain) in these receptor tyrosine kinases are indicated
on the right side of the figure. Cys, cysteine; EGF, epidermal growth factor; PDGF, platelet-derived growth factor. 2_120 76 (64)
Схема. Молекулярные механизмы индуцированной лигандом детерминации рецепторов = Molecular mechanisms of ligand-induced dimerization of receptors.
Примечание: Figure 5-2 Molecular mechanisms of ligand-induced dimerization of receptors. In the example of platelet-derived growth factor (left), the ligand is dimeric
and contains two receptor-binding sites.8,9 In the case of growth hormone (right), a single ligand molecule contains two binding sites so that it can bind
simultaneously to two receptor molecules. 2_120 77 (65)
Схема. Гипотетический механизм запускаемой лигандом активации тирозинкиназой инсулинового рецептора = Hypothetical mechanism for ligand-stimulated activation of the insulin receptor tyrosine kinase.
Примечание: Figure 5-3 Hypothetical mechanism for ligand-stimulated activation of the insulin receptor tyrosine kinase. Phosphorylation of tyrosine residues in the
activation loop leads to activation of the insulin receptor tyrosine kinase. The model is based on the three-dimensional structure of the isolated insulin
receptor tyrosine kinase as determined by x-ray crystallography.19,20,23 In the inactive insulin receptor kinase (left), Tyr1162 blocks the active site so that
substrates cannot bind. When the tyrosine residues in the activation loop (including Tyr1162) become phosphorylated (right), pTyr1162 moves out of the way;
the conformational change allows binding of adenosine triphosphate (ATP) and protein substrate so that the kinase reaction can proceed. 2_120 78 (66)
Схема. Пути потоков информации от инсулиновых рецепторов = Simplified model of signaling pathways downstream from the insulin receptor.
Примечание: Figure 5-4 Simplified model of signaling pathways
downstream from the insulin receptor. Insulin binds
to the insulin receptor, activating the receptor tyrosine
kinase to phosphorylate tyrosine residues on
insulin receptor substrates (IRSs) including IRS1 and
IRS2.31 The phosphotyrosine residues in the IRS molecules
bind to SRC homology 2 (SH2) domains in
molecules such as growth factor receptor–binding
protein 2 (GRB-2) and the p85 regulatory subunit of
phosphatidylinositol (PI) 3-kinase (PI3K). These SH2
domain–containing proteins initiate two distinct
branches of the signaling pathway. Activation of PI3K
leads to activation of phosphoinositide-dependent
kinases (PDKs) 1 and 2, which activate multiple
protein kinases, including Akt/protein kinase B, atypical
protein kinase C (PKC) isoforms, and serum- and
glucocorticoid-induced protein kinases (Sgk).55 GRB2
interacts with mSOS, a guanine nucleotide exchange
factor that activates Ras.56 Activation of Ras triggers
a cascade of protein kinases, leading to activation of
mitogen-activated protein (MAP) kinase. Shc, SRC
homology domain–containing protein. 2_120 80 (68)
Схема. Механизм действия рецептора серинкиназ = Mechanism of action for receptor serine kinases.
Примечание: Figure 5-7 Mechanism of action for receptor serine kinases. Binding of dimeric ligand to the type II receptor (RII) subunit triggers assembly of the receptor
into the heterotetrameric [(RI)2(RII)2] state. RII transphosphorylates the type I receptor (RI), thereby activating phosphorylation of the receptor-regulated
SMAD (R-Smad) protein that is bound to the SMAD anchor for receptor activation (SARA) in endosomes. The phosphorylated R-Smad associates with a
co-mediator SMAD (Co-Smad). Eventually, the R-Smad is translocated into the nucleus, where it binds to DNA, enabling it to regulate gene transcription.
The inhibitory SMAD (I-Smad) also can bind to the activated receptor, promoting ubiquitination and degradation of the receptor. P, phosphorylation; Smurf,
SMAD ubiquitination regulatory factor. 2_120 80 (68)
Схема. Цитокиновые рецепторы, построенные из нескольких субъединиц и связанные с одной или более Янус-киназ (семейство тирозинкиназ) = Cytokine receptors are composed of multiple subunits and bind to one or more members of the Janus kinase (JAK) family of tyrosine kinases.
Примечание: Figure 5-8 Cytokine receptors are composed of multiple subunits and bind to one or more members of the Janus kinase (JAK) family of tyrosine kinases.
A, Growth hormone (GH), like prolactin and leptin, binds to growth hormone receptor (GHR) homodimers and activates JAK2. B, Interferon-г (IFNг)
homodimers bind to their ligand-binding гR1 subunits. The гR2 subunits are then recruited, leading to activation of JAK1, which binds to the гR1 subunit, and
JAK2, which binds to the гR2 subunit. Both subunits and both JAKs are necessary for responses to IFNг. C, Interleukin 2 (IL-2) binds to receptors composed
of three subunits: a гc subunit shared with receptors for IL-4, -7, -9, -15, and -21; an IL-2Rв subunit shared with the IL-15 receptor; and a noncytokine receptor
subunit, IL-2Rб. IL-2 activates JAK3, bound to the гc subunit, and JAK1, bound to IL2-Rв. Extracellular regions of homology are indicated by the black
lines and colored patterns. Intracellular regions of homology are indicated by the small white boxes. Identical subunits are indicated by identical colors. 2_120 83 (71)
Схема. Цитокины активируют переносчики сигналов и активаторы транскрипции = Cytokines activate signal transducers and activators of transcription (STATs).
Примечание: Figure 5-9 Cytokines activate signal transducers and activators of transcription (STATs). STAT proteins are latent cytoplasmic transcription factors. STATs
bind through SRC homology 2 (SH2) domains to one or more phosphorylated tyrosines (P) in activated receptor–Janus kinase (JAK) complexes. Once bound,
STATs themselves are tyrosyl phosphorylated, presumably by the receptor-associated JAKs. STATs then dissociate from the receptor-JAK complex, homodimerize
or heterodimerize with other STAT proteins, move to the nucleus, and bind to gamma-activated sequence-like elements (GLEs) in the promoters of
cytokine-responsive genes. P, phosphorylation. (Adapted from J. Herrington, with permission.) 2_120 84 (72)
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Санкт-Петербург, Россия, 1996-2015
Разрешается некоммерческое цитирование материалов данной энциклопедии при условии
полного указания источника заимствования: имени автора, названия и WEB-адреcа данной энциклопедии
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