Lect. 11 - Signaling Pathways Flashcards Preview

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Flashcards in Lect. 11 - Signaling Pathways Deck (33):

how are signal transduction pathways established?

when a ligand (signaling molecule) binds to a receptor


result of signal transduction pathway

signal being transmitted to the nucleus of a responding cell - responding cell produces gene products that influence the developmental pathway of a cell


Transforming Growth Factor-beta Superfamily (TGF-B1)

disulfide linked dimer; consists of a large proregion and a bioactive region


what forms the dimer in TGF-B1

two bioactive regions after being cleaved from the proregion


what is the purpose of the proregion in TGF-B1 after begin cleaved?

they complex w/ the bioactive dimer to maintain it in a latent form


When does activation occur in TGF-B1?

when the proregions are separated from the bioactive dimer


what part of TGF-B1 functions as the signaling molecule?

bioactive dimer


bone morphogenic proteins

encompasses 15 members w/i TGF-B1 superfamily


what are the modes of action of the bone morphogenic proteins?

inhibit other processes in the embryo, often by being inhibited by other molecules; bind to bioactive dimers and prevent them from binding to receptors


Fibroblast Growth Factor Family number of members

22 members;


FGF family means of regulation

modification of interaction w/ heparan proteoglycans in receptor complex; regulation at membrane of responding cell via transmembrane proteins; regulation by molecules that complex w/ signal transduction machinery


Hedgehog Family

related to the segment polarity molecules in Drosophila; include desert, indian, sonic hedgehog


Wnt Family

includes 18 members in the mouse; related to segment polarity genes in drosophila; often interact w/ components of extracellular matrix; different roles in various vertebrate classes


cell surface receptors w/ intrinsic protein kinase activity

includes receptors for FGF (cytoplasmic domain possesses tyrosine kinase activity) and TGF-beta factors (cytoplasmic domain possesses serine/threonine kinase activity


in the delta-notch pathway, which signal molecule is on the dominant cell?



in delta-notch pathways what is on the neighboring cell?

notch receptor


Delta-Notch pathway actions

proteolytic cleavage of notch in intracellular domain which then complexes w/ Deltex and enters nucleus; complex binds to suppressor of hairless; notch-deltex-suppressor of hairless complex binds to enhanver of split


what is the result signal from the delta notch pathway?

inhibitory signal represses gene expression


lateral inhibition

type of signaling b/w a dominant cell and neighboring cells; the dominant cell is the one that begins to differentiate along a particular path and expresses delta signaling on its membrane.


what happens in lateral inhibition after delta signaling molecule is expressed on the membrane of the dominant cell?

delta binds notch receptors on neighboring cells and represses genes in them (through delta-notch)


receptor tyrosine kinase pathway is used by what kind of signaling molecules?

FGF and TGF-beta


receptor tyrosine kinase pathway components and actions w/ FGF

FGF binds receptor tyrosine kinase; G protein activated (activates RAS, RAF, MAP kinase, and ERK); ERK translocates to nucleus and activates various TFs


receptor tyrosine kinase pathway components and actions w/ TGF-beta

Tgf-beta bind to serine/threonine kinase receptor type II which dimerizes w/ receptor type I (activates R-Smad and Co-Smad); Smad dimer translocates to nucleus and binds to co-factors which can then bind to regulatory factors


Hedgehog pathway

Shh + cholesterol then translocated to cell surface via Dispersed; it inhibited the inhibitory actions of Patched on Smoothened on target cell


In the hedgehog pathway, what is the result of getting an uninhibited smoothened?

it signals the release of transcription Gli from a compelx on microtubules and Gli translocates to the nucleus to influence gene expression


Wnt signaling pathway

Wnt binds to Frizzled on target cell; frizzled interacts w/ disheveled; disheveled prevents degradation of B-catenins by the destruction complex; b-catenins translocate to nucleus and activate Tfs


What is found in the absence of the Wnt?

beta-catenins are bound to an intracellular destruction complex w/i the target cell



small noncoding RNAs that influence gene expression


what are the two major groups of miRNAs

Piwi-interacting RNAs (piRNAs) and endogenous small interfering RNAs (endo-siRNAs)


piwi-interactingRNAs (piRNAs)

act during gametogenesis (esp. spermatogenesis)



expressed in somatic tissues throughout development


miRNA pathway

double helical precursor w/ hairpin loop is cleaved by Dicer and the formed miRNA is complexed w/ an Argonaute (AGO) protein; complex cleaves target mRNA molecule inactivating it


retinol pathway

retinol binds RBP and complex binds to a membrane RBP; retinol is released and binds CRBP-1; RA is bound to CRABP-1 and translocated to nucleus; RA binds dimer RXR-RAR which binds RARE which activates transcription