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Related Concept Videos

Intracellular Signaling Cascades01:24

Intracellular Signaling Cascades

Once a ligand binds to a receptor, the signal is transmitted through the membrane and into the cytoplasm. The continuation of a signal in this manner is called signal transduction. Signal transduction only occurs with cell-surface receptors, which cannot interact with most components of the cell, such as DNA. Only internal receptors can interact directly with DNA in the nucleus to initiate protein synthesis. When a ligand binds to its receptor, conformational changes occur that affect the...
Intracellular Signaling Cascades01:24

Intracellular Signaling Cascades

Once a ligand binds to a receptor, the signal is transmitted through the membrane and into the cytoplasm. The continuation of a signal in this manner is called signal transduction. Signal transduction only occurs with cell-surface receptors, which cannot interact with most components of the cell, such as DNA. Only internal receptors can interact directly with DNA in the nucleus to initiate protein synthesis. When a ligand binds to its receptor, conformational changes occur that affect the...
Yeast Signaling01:28

Yeast Signaling

Yeasts are single-celled organisms, but unlike bacteria, they are eukaryotes (cells with a nucleus). Cell signaling in yeast is similar to signaling in other eukaryotic cells. A ligand, such as a protein or a small molecule released from a yeast cell, attaches to a receptor on the cell surface. The binding stimulates second-messenger kinases to activate or inactivate transcription factors that further regulate gene expression. Many of the yeast intracellular signaling cascades have similar...
Calmodulin-dependent Signaling01:16

Calmodulin-dependent Signaling

Calmodulin (CaM) is a calcium-binding protein in eukaryotes that controls various calcium-regulated cellular processes. It has four calcium-binding sites that bind calcium to form the calcium-calmodulin ( Ca2+-CaM) complex. GPCR stimulation increases the calcium levels in the cells that bind to CaM and induces a conformational change.
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Microtubules in Signaling01:22

Microtubules in Signaling

The primary cilium, made up of microtubules, acts as antennae on the cell surfaces for relaying external stimuli into the cells. These fine hair-like structures are present, generally one per cell. These are non-motile cilia in a 9+0 microtubules arrangement, where the central pair of microtubules are absent. The primary cilia arise from the basal body embedded in the cell membrane. Intraflagellar transport (IFT) carries requisite proteins from the cytoplasm to the cilium because the primary...
Amplifying Signals via Second Messengers01:15

Amplifying Signals via Second Messengers

Many receptor binding ligands are hydrophilic; they do not cross the cell membrane but bind to cell-surface receptors. Thus, their message must be relayed by second messengers present in the cell cytoplasm. There are several second messenger pathways, each with its own way of relaying information. For example, the G protein-coupled receptors can activate both phosphoinositol and cyclic AMP (cAMP) second messenger pathways. The phosphoinositol pathway is active when the receptor induces...

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Imaging G-protein Coupled Receptor (GPCR)-mediated Signaling Events that Control Chemotaxis of Dictyostelium Discoideum
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Published on: September 20, 2011

Cyclic-nucleotide signalling in protozoa.

Matthew K Gould1, Harry P de Koning

  • 1Biomedical Research Centre, Institute of Infection, Immunity & Inflammation, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow, UK.

FEMS Microbiology Reviews
|January 13, 2011
PubMed
Summary

Protozoan cyclic nucleotide signaling pathways, including adenylyl cyclases and phosphodiesterases, differ significantly from mammalian systems. Understanding these unique pathways is crucial for identifying novel drug targets in parasitic protozoa.

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Area of Science:

  • Parasitology
  • Molecular Biology
  • Biochemistry

Background:

  • Signal transduction in mammalian systems is well-understood, but protozoan signaling pathways, particularly cyclic nucleotide metabolism, remain largely unexplored.
  • Protozoan parasites possess unique signaling components distinct from mammals, as evidenced by genomic data.
  • Kinetoplastids lack mammalian Class I adenylyl cyclases (ACs) and G-protein subunits, while Apicomplexan AC and guanylyl cyclase (GC) exhibit unusual bifunctional characteristics.

Purpose of the Study:

  • To summarize existing literature on cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) signaling in protozoa.
  • To provide an overview of protozoan cyclases, phosphodiesterases (PDEs), and cyclic-nucleotide-dependent kinases.
  • To highlight the differences between protozoan and mammalian cyclic nucleotide signaling pathways.

Main Methods:

  • Literature review of studies on protozoan cyclic nucleotide metabolism.
  • Comparative analysis of signaling pathway components between protozoa and mammals.
  • Examination of genomic data for identifying signaling molecules in protozoa.

Main Results:

  • Protozoan ACs possess a single transmembrane domain, a conserved catalytic domain, and a variable extracellular domain, but lack identified receptor ligands.
  • Apicomplexan AC and GC may be bifunctional, incorporating ion channel or P-type ATPase-like domains.
  • Phosphodiesterases (PDEs) and cyclic-nucleotide-activated protein kinases are conserved but largely insensitive to mammalian inhibitors, with some PDEs emerging as potential drug targets.

Conclusions:

  • Protozoan cyclic nucleotide signaling pathways are significantly divergent from those in mammals.
  • The unique nature of these pathways presents challenges but also opportunities for therapeutic intervention.
  • Further research into protozoan signaling components, particularly PDEs, is warranted for drug development against parasitic diseases.