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M2MUnit4 > Cilia > Flashcards

Cilia Flashcards

1
Q

What are the major domains that build the cilium?

A

Centriole/basal body; axoneme; transition zone; ciliary membrane; and intraflagellar transport (IFT) machinery

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2
Q

What are basal bodies?

A

Core anchors from which cilia are formed.

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3
Q

What is the structure of basal bodies?

A

Cylinder shaped structures formed from nine triplet microtubules (A-B-C tubules). Typically 150-200 nm in diameter and 500 nm in length. Polarized structure is formed beginning at the proximal-end and the distal-end is responsible for nucleating the cilium.

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4
Q

What is the axoneme?

A

Structural skeleton of the cilium (scaffolding). Alo provide the tracks for movement within the cilia

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5
Q

What is the structure of the axoneme?

A

Formed from doublet microtubules (A-B tubules) that assemble from the A- and B-tubules of the basal body. The microtubules are polar polymers and the plus-ends reside at the ciliary tip. Cilium lengths range from

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6
Q

What is the transition zone?

A

Links the basal body to the axoneme and to the ciliary membrane. Also considered the “gatekeeper” because it limits the diffusion of membrane and soluble proteins into and out of the cilium.

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7
Q

Why is transition zone important?

A

The “gatekeeper.” Ensures the ciliary membrane is a distinct compartment for cellular signaling. If there are absent/defective proteins in transition zone it often leads to ciliary diseases.

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8
Q

What is the ciliary membrane?

A

Continuous with the cellular plasma membrane BUT this membrane is compartmentalized (by the transition zone) so that it is a compositionally distinct membrane with unique phospholipids and receptor molecules.

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9
Q

What is intraflagellar transport (IFT)?

A

The mechanism by which cargo is transported along the axoneme. Either to or from the cilia (important for assembly; maintenance; movement of signaling components)

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10
Q

Which proteins direct movement toward to the ciliary tip (anterograde)?

A

Kinesin motors (Kinesin-2 family) and the IFT-B protein complex

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11
Q

Which proteins direct movement away from the ciliary tip (retrograde)?

A

Cytoplasmic dynein 2 motor driven transport with the IFT-A protein complex

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12
Q

What are the two phases of ciliogenesis?

A

1: centrioles/basal bodies are assembled 2: formation of the cilium

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13
Q

Which structure is important for the formation of basal bodies AND centrosomes?

A

centrioles

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14
Q

Upon ciliogenesis; which of the two centrioles function as the basal body?

A

The older of the two (the mother centriole)

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15
Q

When does centriole duplication occur?

A

During the G1 to S-phase cell cycle boundary (coincident with DNA synthesis).

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16
Q

When does ciliogenesis normally occur?

A

During G1 (or G0)

17
Q

How does ciliogenesis occur?

A

Asembly from the mother centriole of the centriole pair. Begins when the distal end of the basal body is capped by a ciliary vesicle. Microtubule doublets then assemble into the ciliary vesicle before the entire structure fuses with the plasma membrane of the cell.

18
Q

How is ciliogenesis accomplished beyond the primary cilia formation (which is linked to the cell cycle)?

A

Basal body assembly is uncoupled from the cell cycle and replication is amplified to facilitate the multiple basal bodies required for ciliogenesis in multi-ciliated epithelial cells.

19
Q

How is motility produced in cilia?

A

Axonemal dynein dependent sliding motion between the doublet microtubules of the ciliary axoneme.

20
Q

What is the typical microtubule arrangement of motile cilia?

A

Usually 9+2 microtubule arrangement (9 doublets organized around a central pair of singlets). BUT not all motile cilia have the central pair microtubules

21
Q

What is the distinguishing factor between motile and immotile cilia?

A

The presence of axonemal dynein arms between the doublet microtubules. Non-motile; sensory or primary cilia possess a 9+0 microtubule arrangement and lack axonemal dynein arms.

22
Q

Why are cilia used for cell signaling?

A

Cilium concentrates the signal with a high receptor surface to volume ratio. Signal is localized and polarized within discrete domains of the cell. Receptors are positioned away from interfering cellular domains. Cilium can function as a mechanical detector of flow.

23
Q

What is one important pathway that fuctions through cilia?

A

The hedgehog (Hh) signaling pathway.

24
Q

What does the Hh pathway related to?

A

Activation and repression of the target of the Hh paracrine signaling pathway (Gli (glioma tumor) transcriptional activator) requires cilia.

25
Q

What are some downstream targets of Hh signaling?

A

Limb formation. Bone formation and homeostasis. Neurogeneis

26
Q

What are common characteristics of ciliopathies?

A

Rare. Pleiotropic. Overlapping. Structural. Diverse. Genetically complex

27
Q

What is Bardet-Biedl Syndrome (BBS)?

A

An autosomal recessive ciliopathy that is caused by the mutation of at least 19 genes.

28
Q

What do BBS proteins do?

A

Participate in a protein complex that is required for vesicle transport within the cilium.

29
Q

What are symptoms of BBS?

A

Photoreceptor degeneration. Anosmia. Mental retardation / Developmental delay. Neural tube defects. Obesity. Hypogonadism. Kidney defects. Polydactyly. Diabetes. Situs inversus

30
Q

What is polycystic kidney disease (PKD)?

A

Autosomal dominant OR recessive ciliopathy

31
Q

What causes ARPKD?

A

Fibrocystin mutations

32
Q

What causes ADPKD?

A

Mutations in polycystin-1 and polycystin-2

33
Q

What are the mutations seen in PKD related to?

A

Genes encode channel proteins that are responsible for calcium signaling. These channels sense mechanical flow of urine in the kidney lumen to transduce calcium signaling.

34
Q

What are symptoms of PKD?

A

Renal cysts; liver and pancrease cysts; intracranial aneurysms

M2MUnit4 (6 decks)

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