Document Detail


Adaptor protein complex 2-mediated, clathrin-dependent endocytosis, and related gene activities, are a prominent feature during maturation stage amelogenesis.
MedLine Citation:
PMID:  23044750     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Molecular events defining enamel matrix removal during amelogenesis are poorly understood. Early reports have suggested that adaptor proteins (AP) participate in ameloblast-mediated endocytosis. Enamel formation involves the secretory and maturation stages, with an increase in resorptive function during the latter. Here, using real-time PCR, we show that the expression of clathrin and adaptor protein subunits are upregulated in maturation stage rodent enamel organ cells. AP complex 2 (AP-2) is the most upregulated of the four distinct adaptor protein complexes. Immunolocalization confirms the presence of AP-2 and clathrin in ameloblasts, with strongest reactivity at the apical pole. These data suggest that the resorptive functions of enamel cells involve AP-2 mediated, clathrin-dependent endocytosis, thus implying the likelihood of specific membrane-bound receptor(s) of enamel matrix protein debris. The mRNA expression of other endocytosis-related gene products is also upregulated during maturation including: lysosomal-associated membrane protein 1 (Lamp1); cluster of differentiation 63 and 68 (Cd63 and Cd68); ATPase, H(+) transporting, lysosomal V0 subunit D2 (Atp6v0d2); ATPase, H(+) transporting, lysosomal V1 subunit B2 (Atp6v1b2); chloride channel, voltage-sensitive 7 (Clcn7); and cathepsin K (Ctsk). Immunohistologic data confirms the expression of a number of these proteins in maturation stage ameloblasts. The enamel of Cd63-null mice was also examined. Despite increased mRNA and protein expression in the enamel organ during maturation, the enamel of Cd63-null mice appeared normal. This may suggest inherent functional redundancies between Cd63 and related gene products, such as Lamp1 and Cd68. Ameloblast-like LS8 cells treated with the enamel matrix protein complex Emdogain showed upregulation of AP-2 and clathrin subunits, further supporting the existence of a membrane-bound receptor-regulated pathway for the endocytosis of enamel matrix proteins. These data together define an endocytotic pathway likely used by ameloblasts to remove the enamel matrix during enamel maturation.
Authors:
Rodrigo S Lacruz; Steven J Brookes; Xin Wen; Jaime M Jimenez; Susanna Vikman; Ping Hu; Shane N White; S Petter Lyngstadaas; Curtis T Okamoto; Charles E Smith; Michael L Paine
Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural    
Journal Detail:
Title:  Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research     Volume:  28     ISSN:  1523-4681     ISO Abbreviation:  J. Bone Miner. Res.     Publication Date:  2013 Mar 
Date Detail:
Created Date:  2013-02-18     Completed Date:  2013-08-29     Revised Date:  2014-03-09    
Medline Journal Info:
Nlm Unique ID:  8610640     Medline TA:  J Bone Miner Res     Country:  United States    
Other Details:
Languages:  eng     Pagination:  672-87     Citation Subset:  IM    
Copyright Information:
Copyright © 2013 American Society for Bone and Mineral Research.
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MeSH Terms
Descriptor/Qualifier:
Adaptor Protein Complex 2 / physiology*
Amelogenesis*
Animals
Antigens, CD63 / genetics
Blotting, Western
Cells, Cultured
Endocytosis / physiology*
Lysosomes / metabolism
Mice
Mice, Knockout
Polymerase Chain Reaction
Rats
Rats, Wistar
Transcription, Genetic
Grant Support
ID/Acronym/Agency:
DE013404/DE/NIDCR NIH HHS; DE019629/DE/NIDCR NIH HHS; R01 DE013404/DE/NIDCR NIH HHS; R01 DE019629/DE/NIDCR NIH HHS
Chemical
Reg. No./Substance:
0/Adaptor Protein Complex 2; 0/Antigens, CD63; 0/Cd63 protein, mouse
Comments/Corrections

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