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Physio Exam 3 - Endocrine > 15 | Hormone/Receptor > Flashcards

15 | Hormone/Receptor Flashcards

1
Q

hormone

A

substance secreted directly into the blood
by specialized cells
in response to a specific stimulus
which then influence other type(s) of cells

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2
Q

hormone-receptor interaction characteristics (6)

A

highly specific
high affinity
saturable (max binding capacity)
simple, bimolecular, reversible reaction
only in responsive tissue
may/may not need full saturation for full bio response

[GPCR, kinase-linked rec, steroid rec, thyroid hormone rec (not TSH)]

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3
Q

dissociation constant Kd

equation, 3 characteristics

A

Kd=[H][R]/[HR]
when [H]=Kd half of the receptors are bound to hormone
[H]*10 (above Kd) – 90% receptor occupancy
[H]/10 (of Kd) – 10% receptor occupancy

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4
Q

hormone types that interact with cell surface receptors (2)

A

peptide hormones
amines
-too polar, too large

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5
Q

cell surface receptor groups (2)

A

7 membrane-spanning domains (GPCR)

single membrane-spanning domain (enzyme linked)

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6
Q

role of G-proteins

A

membrane associated guanine nucleotide binding proteins
couple hormone binding to a receptor to effector modulation
Ga subunit is a GTPase (GDP+Pi)

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7
Q

G-protein + adenylase cyclase

mechanism

A
  • activation of AC mediated by Gsa (regulatory, stimulatory)
  • AC catalyzes formation of cAMP
  • cAMP activates PKA by binding to regulatory subunits, releasing catalytic subunits
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8
Q

ligands that use cAMP as a secondary messenger (11 + 4)

A 
ACTH
ADH
EPI/NE (catechol B-rec)
glucagon 
glycoprotein hormones (LH, TSH, FSH, hCG) 
histamine 
MSH 
PG's 
PTH 
secretin 
VIP
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9
Q

G-protein + phospholipase C

mechanism

A
  • Gqa activates PLC
  • PLC cleaves PIP2 (membrane associated inositol phospholipid) to DAG + IP3
  • IP3 stimulates release of Ca2+ from storage
  • DAG (retained in membrane) associated with PKC, activates it in presence of Ca2+
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10
Q

phosphoinositol (PI) 3-kinase action

A
  • PIP3-kinase phosphorylates PIP2 to PIP3
  • PIP3 interacts with protein kinases (PDKs)
  • PDKs travel to membrane, activate enzyme Akt
  • Akt can phosphorylate target proteins (i.e. transcription factors)
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11
Q

G-protein + phosphodiesterase

A

Gta (in photoreceptors)
cGMP -> GMP
cAMP -> AMP

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12
Q

1TMD - tyrosine kinase rec

A

intrinsic tyrosine kinase activity

  • binding dimerizes agonist/receptor complex
  • autophosphorylation
  • autophos inc. kinase activity and inc. afficity for associated substrates
  • substrates are phos., con’t signaling
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13
Q

1TMD - serine/threonine kinase rec

A
  • ligand binding, dimerize, phosphorylate cytoplasmic “Smads”
  • Smads regulate gene transcription in the nucleus
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14
Q

1TMD - guanylate cyclase rec

A
  • binding inc cytoplasmic cGMP

- cGMP mediates further action (i.e. PKG)

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15
Q

1TMD - cytokine rec family

A
  • lacks intrinsic enzyme activity
  • associate with soluble cytoplasmic tyrosine kinases (JAKs) with ligand binding/dimerization
  • JAKs/DimRec activated, phos STATs (signal transducers and activators or transcription)
  • STATs dimerize, travel to nucleus
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16
Q

1TMD - MAP kinase paths

A

MAP (mitogen activated protein)

  • cascade of protein kinase reactions
  • roles in cell proliferation in response to GF stimulation
17
Q

receptor-mediated endocytosis

A

hormone/receptor complexes clustered in clathrin-coated pit region

  • invaginate, pinch off, form coated vesicles
  • targets to lysosome for degradation (hormones)
  • receptors typically recycled to PM
18
Q

intracellular rec - ligands

A

steroid hormones (TH, androgens)

  • lipophillic
  • bind to receptors in cytoplasm or nucleus
19
Q

cytoplasmic steroid hormone/receptor complex

A

[steroid hormones - cortisol, aldo - androgens]

  • receptor associated with HSP90, prevent interaction with DNA w/out ligand
  • ligand binding dissociates
  • H/R complexes dimerize, move to nucleus, interact with HREs
20
Q

nuclear steroid hormone/receptor complex

A

[THs, Vit D derivatives)

  • receptors associate with HREs w/out hormone
  • alone, associated with nuclear proteins
  • ligand binding releases nuclear proteins
  • new nuclear proteins can now bind
  • complex can promote activation or suppression of transcription targets
21
Q

hormone response elements (HREs)

A
  • palindromic sequences (inverted repeat)
  • H/R dimerization for interaction
  • binding initiates or suppresses transcription of nearby genes
22
Q

kinase-linked ligands (10)

A 
insulin, IGF-1, EGF, PDGF, GH
mullerian inh substance, inhibin 
ANP
EPO
prolactin
[insulin, growth factors, ANP (no steroids)]
23
Q

intracellular receptor sequence

A

[3 structural domains]
C term hormone binding
central DNA binding (Cys residues, form Zn fingers, recognize specific HRE’s)
variable N term transcription factor binding

24
Q

steroid hormone vs. protein hormone

A

not stored vs. stored
carrier-bound transport vs. soluble
interior rec vs. cell surface rec
passive diffusion into cell vs. receptor mediated endocytosis

25
Q

hormone availability factors (4)

A 
secretion rates 
uptake 
degradation 
[plasma carrier protein]
(free hormone eq. w/ carrier bound)
26
Q

cell sensitivity - negative cooperativity

A

increasing receptor occupancy decreases affinity of remain receptors for a hormone
-modulates hormone action, high cell sensitivity (rec affinity) at low [hormone] and low sensitivity at high [hormone]

27
Q

cell sensitivity - down regulation

A

exposure of cell to high [hormone] concentration can decrease number of cell surface receptors (loss of binding sites)
-can protect cell from intense stimulation

28
Q

cell sensitivity - enzyme activity

A

decreased enzyme activity in one or more enzymes down stream from H/R

29
Q

cell sensitivity - uncoupling of receptor from G-protein (ex)

A

B-adrenergic system
-B-adrenergic kinase (B-ARK) associates with free By at membrane
-B-ARK phosphorylates the receptor
-B-arrestin binds to phosphorylated receptor
-hormone can no longer bind to receptor/interact with G -protein
(inc [hormone], inc [By], inc potential for desensitization)

30
Q

factors influencing cell sensitivity (4)

A

negative cooperatively
down regulation
decreased enzyme activity
G-protein/receptor uncoupling

31
Q

hormone inactivation

peptides, steroids

A

peptide hormones:
-inactivated by proteases on cell surface
-internalized, lysosome degradation
steroid hormones:
-inactivated in liver to polar derivatives filtered by kidney

32
Q

hormone radioimmunoassay

A
  • measurement of nanogram levels of hormone

- competitive binding assay between unlabeled and radio labeled hormone for Ab binding

33
Q

Scatchard analysis

A
  • determine binding constants of hormone receptor interactions
  • determine concentration of receptors
34
Q

androgen insensitivity syndrome

A
  • individual doesn’t synthesize functional androgen receptor
  • XY individual produces testosterone (T)
  • testis produce T, but target tissues don’t receive signal for differentiation
  • no internal or external male genitalia. appears female.
  • at puberty pituitary increase production of LH, stimulates testis to produce more T
  • normally have negative feedback, T inhibits further LH secretion
  • with AIS, T levels rise higher than normal, with no male secondary sex characteristic dev
  • some T is converted to E by aromatase in the periphery, develops female phenotype
35
Q

GPCR ligands (non cAMP linked, 6)

A

GnRH, TRH, alpha-1, ANII, CCK, gastrin

Physio Exam 3 - Endocrine (8 decks)

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