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#extracellular signaling

2 public questions tagged with this topic.

Morphogen Induction-l

Which type of cell signaling involves molecules secreted into the extracellular space and acting on nearby cells?

Paracrine factors are synthesized, modified in secretory pathway by glycosylation and lipidation, released into interstitial fluid and act within hundred micron range via diffusion, receptor-mediated uptake and endocytic degradation. Ligands such as FGFs, Hedgehogs and TGF-beta superfamily bind receptor tyrosine kinases or serine-threonine kinase receptors activating downstream MAPK, PI3K or Smad cascades in adjacent cells, creating short-range patterning and mitogenic effects. Juxtacrine requires membrane contact, autocrine targets same producing cell establishing positive feedback, endocrine travels via circulation to distant targets. Paracrine mode enables local induction and gradient patterning essential for embryonic field organization and tissue homeostasis.

Ref: Alberts, Molecular Biology of the Cell, 6th ed., Chapter 15: Paracrine Signal Diffusion and Gradient.

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Dictyostelium

High extracellular cAMP induces:

High ambient extracellular cAMP acts as positional cue favoring prespore differentiation through sustained protein kinase A activation. At millimolar levels, cAMP saturates desensitization mechanisms, maintaining intracellular messenger elevated, inducing transcription of prespore-specific genes encoding spore coat proteins while repressing prestalk markers. Low-density monolayer experiments show cAMP plus conditioned medium induces prespore markers, whereas DIF-1 alone induces prestalk. High cAMP therefore mirrors posterior slug environment where prespore cells reside. Prestalk formation prefers low cAMP together with DIF-1, vegetative growth requires folate, slug dispersal demands low cAMP oscillations, highlighting dosage-dependent fate specification mechanism.

Ref: Methods in Molecular Biology, Prespore induction by high cAMP - SP70 expression and PKA signaling mechanism.

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