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#juxtacrine signaling

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Morphogen Induction-l

Which of the following is an example of a juxtacrine signaling pathway?

Juxtacrine signaling requires direct membrane apposition where ligand retained on surface of one cell activates receptor on neighboring cell without secretion. Canonical example is Notch-Delta: Delta family ligand on signaling cell binds Notch receptor, inducing proteolytic cleavages by ADAM and gamma-secretase releasing intracellular domain that activates transcription via CSL. BMP-Wnt interaction represents paracrine crosstalk where secreted morphogens antagonize or synergize via extracellular binding, diffusing at distance, not contact-dependent signal. TGF-beta-Smad and FGF-Erk also represent diffusible paracrine with intracellular cascades. Therefore juxtacrine hallmark is cell-contact dependence without extracellular gradient, typified by Notch-Delta lateral inhibition mechanism controlling fate.

Ref: Alberts, Molecular Biology of the Cell, 6th ed., Chapter 15: Juxtacrine versus Paracrine Signaling.

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Induction Morphogen -ll

Which of the following is an example of a juxtacrine signaling pathway?

Juxtacrine signaling requires cell-to-cell contact where membrane-bound ligand on one cell engages receptor on adjacent cell without secretion or diffusion. Notch-Delta interaction exemplifies this: Delta ligand presented on signaling cell binds Notch receptor on receiving cell, triggering ADAM and gamma-secretase cleavage and release of Notch intracellular domain that translocates to nucleus and activates Hes genes via Su(H) complex. BMP, Wnt and Sonic hedgehog are diffusible paracrine morphogens acting at distance via gradient. Contact-dependent Notch-Delta mediates lateral inhibition, boundary formation and binary fate choices during neurogenesis, somitogenesis and lymphocyte development ensuring precise patterning.

Ref: Alberts, Molecular Biology of the Cell, 6th ed., Chapter 15: Notch-Delta Juxtacrine Signaling.

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Induction Morphogen -ll

Which type of signaling involves direct cell-to-cell contact?

Juxtacrine signaling requires direct physical contact between adjacent cells, where membrane-bound ligand presented on one cell surface binds receptor on immediate neighbor without diffusion. Canonical example is Notch-Delta pathway controlling lateral inhibition and binary fate decisions: Delta ligand activates Notch receptor triggering gamma-secretase cleavage and NICD transcriptional regulation that suppresses neural potential in receiving cell. Such contact-dependent communication ensures precise patterning at single-cell resolution without soluble intermediates, distinguishing it from paracrine diffusion over several cell diameters or endocrine circulation through bloodstream. Gap junctions also represent juxtacrine exchange of small metabolites.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 4: Juxtacrine Signaling and Notch-Delta Communication.

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