Cells, whether unicellular organisms or cells within multicellular organisms, respond to signals within their environment. Such signals include mechanical stimuli (light, sound) and chemicals. The origin of chemical stimuli may be the cell itself (autocrine), adjacent cells (paracrine), the plasma membrane of adjacent cells (contact inhibition), or distant cells (endocrine).
Neurotransmission incorporates interaction between neurotransmitters and specific receptor proteins. Cytokines mediate paracrine stimulation, and hormones mediate endocrine stimulation.
Cellular responses to signalling molecules include alterations in gene expression (transcription), alteration of electrophysiological charge, and alteration of metabolic activity of the cell.
Intracellular interactions in prokaryotes
Four kinds of cell interactions can be distinguished:
1) Transfer of a chemical signal from one cell to another. The variety of such transfers is presented in several examples.
2) Signaling by direct physical contact between two cell bodies, which may involve their surfaces or cell appendages, such as fibrils, pili, or flagella (bacterial flagella). Direct physical contact is often involved in cell swarming.
3) Syntrophic metabolism. Schink Syntrophism Among Prokaryotes.
4) Gene transfer from one cell to another.
Eubacterial gene transfer interactions are widespread. Transfer within the Archaea has recently been observed, and their genetics is being developed (Stedman et al., 1999; Whitman et al., 1999). Prokaryotes have three mechanisms for unidirectional gene transfer from a donor to a recipient. These mechanisms are transformation in which naked DNA from the donor is taken up by the recipient, generalized transduction in which a phage has packaged a head-full of donor DNA and injects that DNA into the recipient, and conjugation in which a specialized apparatus (pili) in the donor transfers a long DNA segment directly into a conjugating recipient.
• bacterial interactions • concentration gradients • ion channels • protein pumps • receptor proteins • receptor-mediated endocytosis • GPCRs • GPCR families • hormones • neurotransmission • Nitric Oxide • neuronal interconnections • phosphotransfer-mediated signaling pathways • Protein Kinase Signaling Networks • signaling gradients :
KEGG Encyclopedia : Pathway ABC transporters : Pathway Phosphotransferase system (PTS) : Pathway Two-component system : Pathway MAPK signaling pathway : Pathway Wnt signaling pathway : Pathway Notch signaling pathway : Pathway Hedgehog signaling pathway : Pathway TGF-beta signaling pathway : Pathway VEGF signaling pathway : Pathway Jak-STAT signaling pathway : Pathway Calcium signaling pathway : Pathway Phosphatidylinositol signaling system : Pathway mTOR signaling pathway : Pathway Neuroactive ligand-receptor interaction : Pathway Cytokine-cytokine receptor interaction : Pathway ECM-receptor interaction : Pathway Cell adhesion molecules (CAMs) : Orthology Transporters (+diseases) : Orthology Two-component system : Orthology Receptors and channels (+diseases) : Orthology Cytokines :
Orthology Cell adhesion molecules (CAMs) : Orthology CAM ligands : Orthology CD molecules :
Orthology GTP-binding proteins :