Related Experiment Video
Updated: Aug 1, 2026
08:26
Development of Amelogenin-chitosan Hydrogel for In Vitro Enamel Regrowth with a Dense Interface
Published on: July 10, 2014
Cyclic AMP-receptor proteins in the enamel matrix
M I Mednieks1, N N Merheb, D R Eisenmann
1Department of Oral Biology, University of Illinois College of Dentistry, Chicago, USA. mednieks@nsol.uchc.edu
Connective Tissue Research
|November 4, 2000
Summary
Cyclic AMP receptor proteins (cARP) are found in ameloblasts and secreted into the enamel matrix during tooth development. This discovery offers new insights into enamel formation and protein kinase A pathways.
Area of Science:
- Cell Biology
- Developmental Biology
- Biochemistry
Background:
- Cyclic AMP receptor proteins (cARP) function as regulatory subunits of protein kinase A (PKA) intracellularly.
- cARPs are also recognized as secretory products in various cell types.
Purpose of the Study:
- To investigate the presence and secretion of cARPs by ameloblasts.
- To determine the localization of cARPs within the enamel matrix of the rat incisor.
Main Methods:
- Photoaffinity labeling
- Western blotting
- Immunogold cytochemistry
Main Results:
- cARPs were detected in secretory ameloblasts, including Tomes' Processes, secretory granules, and the Golgi region.
- Specific labeling for cARPs was observed in the enamel matrix, particularly during early maturation, but not in dentin.
- Increased nuclear labeling intensity for cARPs was noted in maturation ameloblasts compared to secretory ameloblasts.
Conclusions:
- Cyclic AMP receptor proteins are expressed by ameloblasts and secreted into the developing enamel matrix.
- The precise roles of cARPs in enamel mineralization and PKA pathway involvement in enamel protein synthesis require further investigation.
Related Concept Videos
01:24Intracellular 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...
01:15Amplifying 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...
01:09GPCRs Regulate Adenylyl Cylase Activity
Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of cells.
Two...
Two...
01:25cAMP-dependent Protein Kinase Pathways
Cyclic Adenosine Monophosphate (cAMP) is an essential second messenger that activates protein kinase A (PKA) and regulates various biological processes. A single epinephrine molecule binds to GPCR and activates several heterotrimeric G proteins, each stimulating multiple adenylyl cyclase, amplifying the signal, and synthesizing large numbers of cAMP molecules. Small changes in cAMP concentration affect PKA activity. The binding of four cAMP molecules induces a conformational change in PKA,...
01:27Feedback Regulation of Calcium Concentration
Calcium is an essential signaling molecule required for various cellular functions. Calcium pumps and ion channels on cell and organellar membranes, such as those on the endoplasmic reticulum (ER), regulate calcium concentrations inside the cell. They remain closed, keeping the cytosolic calcium levels low at a resting state.
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...
Various transmembrane receptors, such as G protein-coupled receptors (GPCRs), elicit a response to extracellular signals by increasing cytosolic calcium. Activated GPCRs...
01:16Calmodulin-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,...
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...