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Hematological Genetics > Iron Metabolism & Absorbtion > Flashcards

Iron Metabolism & Absorbtion Flashcards

1
Q

What is Fe used for?

A

Readily exchanges e⁻, ideal catalyst for redox rxns, important role in e⁻ transport chain, O₂ transport, heme, stored in ferritin, myoglobin & enzymes

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2
Q

Where is Fe stored?

A

Much in RBCs some stored in ferritin, myoglobin & enzymes

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3
Q

What regulates bodies Fe content?

A

Modulating absorption (intestine)

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4
Q

What is the regulated pathway for Fe excretion?

A

There isn’t one

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5
Q

What does too much Fe do?

A

It’s interaction w/ O₂ can promote cellular damage

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6
Q

What is the total amount of Fe found in the body and how much is in RBCs?

A

3-5 g total, 2.7 g in RBCs

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7
Q

How much Fe is needed daily to support Hb production?

A

25 mg

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8
Q

What is the distribution of Fe in a normal man?

A

Hemoglobin: 67%
Storage Fe: 27%
Myoglobin: 5%
Fe-requiring proteins: 1%

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9
Q

In what forms does Fe exist?

A

Fe2+ (ferrous) Fe3+ (ferric)

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10
Q

In what forms does Fe exist?

A

Fe²⁺ (ferrous) Fe³⁺ (ferric)

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11
Q

What is ferritin, its location, and purpose?

A

Intracellular protein found in most cells that binds thousands of Fe3+/molecule

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12
Q

What is ferritin, its location, and purpose?

A

Intracellular protein found in most cells that binds thousands of Fe³⁺/molecule

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13
Q

Where is excess Fe mainly stored?

A

Liver, lunges, pancreas

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14
Q

What are the Fe transport proteins?

A

Ferrireductase, DMT1 (divalent transporter-1), Hephaestin, Ferroportin

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15
Q

In what form is dietary Fe?

A

Fe³⁺ (ferric)

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16
Q

What reduces ferric Fe to the ferrous form?

A

Dcytb (duodenal cytochrome-like b, Fe³⁺→Fe²⁺, ferric→ferrous

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17
Q

What reduces ferric Fe to the ferrous form?

A

Dcytb (duodenal cytochrome-like b, Fe³⁺→Fe²⁺, ferric→ferrous

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18
Q

What transports Fe outside the cell into the blood?

A

Ferroportin, basolateral surface → blood

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19
Q

What does ferroportin require to perform transport?

A

Ferroxidase (Hephaestin)

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20
Q

What carries Fe from the blood to the bone marrow?

A

Transferrin

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21
Q

What must first happen for Fe to be transported by transferrin into the bone marrow?

A

Fe must be changed from ferrous to ferric, Fe³⁺→Fe²⁺

22
Q

What must first happen for Fe to be transported by transferrin into the bone marrow?

A

Fe must be changed from ferrous to ferric, Fe³⁺→Fe²⁺

23
Q

What does transferrin do?

A

Binds 1-2 Fe³⁺/molecule w/ high affinity and carries Fe blood → tissues in a non-toxic form

24
Q

What size and what type of protein is transferrin?

A

76 kDa serum glycoprotein

25
Q

Describe tranferrin-receptor mediated endocytosis?

A

Transferrin binds Fe³⁺→ transferrin binds transferrin-R (TfR)→ endocytosed into endosome w/ clathrin coat→ clathrin coat removed→ proton pump ↓ pH to 5.5→ Fe released→ endosome fusses with cell exterior→ pH ↑ to 7.4→ TfR releases transferrin

26
Q

What is the “kiss & run” hypothesis?

A

The idea that the TfR mediated transfer of Fe to the MT is so efficient that the endosome briefly docks “kisses” the MT transfers Fe directly & leaves “runs”, No cytoplasmic transport protein needed

27
Q

What is the function of Steap3 ferroreductase?

A

Reduces Fe³⁺→Fe²⁺ in the endosome

28
Q

What is the function of DMT1?

A

Transports Fe²⁺ out of endosome

29
Q

What are causes of Fe deficiency?

A

Insufficient dietary Fe, menstration, Aspirin abuse

30
Q

What are symptoms of Fe deficiency?

A

Gi tract ulcers, hypochromic microcytic anemia

31
Q

What is the treatment for Fe deficiency?

A

Dietary Fe supplement

32
Q

What are causes of Fe overloading?

A

Hereditary hemochromatosis, repeated blood transfusions (conditional Fe overloading)

33
Q

What is the clinical definition of hereditary hemochromatosis?

A

Organ dysfuntion due to Fe orverload

34
Q

What is the genetic definition of hereditary hemochromatosis?

A

Autosomal recessive mutation in HFE gene

35
Q

What is the functional definition of hereditary hemochromatosis?

A

Malregulation of Fe uptake & export by entreocyte

36
Q

What is the clinical presentation of hereditary hemochromatosis?

A

Elevated total body Fe w/ cell injury, liver damage, diabetes, heart failure, >400ng/mL, visible Fe overloading in liver

37
Q

What is the function of the HFE protein and where is it found?

A

Binds transferrin-R

38
Q

What is the role of HFE in hereditary hemochromatosis?

A

Mutation of HFE causes hereditary hemochromatosis

39
Q

What is the treatment for hereditary hemochromatosis?

A

blood letting 1 unit blood/week up to 80 weeks → 1 unit/every other month, ExJade

40
Q

What does ExJade do and what are its side effects?

A

Fe chelator, can cause nephrotic syndrome & death

41
Q

What is the role of Hfe in signal transduction?

A

It is bound to Tfr1 until Fe competitively outbinds it → Hfe binds Tfr2 → induces hepcidin expression

42
Q

What the relationship b/t Fe levels and hepcidin expression?

A

Fe replete= ↑ hepcidin

Fe deplete= ↓ hepcidin

43
Q

What is the role of Hfe in signal transduction?

A

It is bound to Tfr1 until Fe competitively outbinds it → Hfe binds Tfr2 → ↑ hepcidin expression

44
Q

Describe the role of bone morphogenic protein in hepcidin signaling?

A

↑Fe= ↑BMP6, BMP binds BMPR→R-SMAD binds SMAD4→ SMAD complex binds hepcidin promoter→ ↑ hepcidin

45
Q

What is juvenile hemochromatosis?

A

Fe overloading disease that manifests in the 2nd decade of life

46
Q

What is the role of hemojuvelin (HJV) in juvenile hemochromatosis?

A

↓HJV→ ↓BMPR effectiveness, Hemojuvelin is co-receptor for BMPR that enhances BMPR activity

47
Q

What is the role of hepcidin antimicrobial peptide (HAMP) gene in juvenile hemochromatosis?

A

↓HAMP→ ↓hepcidin, HAMP makes hepcidin, rare condition

48
Q

What is the cause of non-hereditary hemochromatosis?

A

Blood transfusions

49
Q

What is the treatment for non-hereditary hemochromatosis?

A

ExJade

50
Q

What does the transmembrane serine-protease (TMPRSS6) do and where is it made?

A

↑TMPRSS6→ ↓HJV, made in the liver

Hematological Genetics (8 decks)

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