Calcium transport in human salivary glands: a proposed model of calcium secretion into saliva.
Salivary calcium plays a vital role in bio-mineralization of dental enamel and exposed dentin. In order to elucidate the yet unknown cellular and molecular mechanisms of calcium secretion in human salivary glands the presence of various relevant plasma membrane transport systems for calcium were investigated. Using an RT-PCR approach, expression of the epithelial calcium channel (CaT-Like), the calcium binding protein (calbindin-2), the endoplasmic reticulum pumps (SERCA-2 and -3), and the plasma membrane calcium ATPases (PMCA-1, -2, and -4), were found in parotid and submandibular glands. Immunohistochemistry revealed that CaT-Like is located in the basolateral plasma membrane of acinar cells; while calbindin-2, SERCA-2 and SERCA-3 were found inside the acinar cells; and PMCA-2 was found in the apical membrane and in the secretory canaliculi between the cells. Based on these findings, we propose the following model of calcium secretion in human salivary glands: (1) calcium enters the acinar cell at the basolateral side via calcium channel CaT-Like (calcium influx); (2) intracellular calcium is taken up into the endoplasmic reticulum by SERCA-2 and possibly SERCA3 or bound to calbindin-2 (intracellular calcium pool); and (3) calcium is secreted by PMCAs at the apical plasma membrane (calcium efflux).
Homann
Veronika
V
Abteilung Epithelphysiologie, Max-Planck-Institut für molekulare Physiologie, 44139, Dortmund, Germany.
Kinne-Saffran
Evamaria
E
Arnold
Wolfgang H
WH
Gaengler
Peter
P
Kinne
Rolf K-H
RK
D000328:Adult; D064032:Calbindin 2; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000096:biosynthesis; D002135:Calcium-Binding Proteins / Q000096:biosynthesis*; D005786:Gene Expression Regulation; D006801:Humans; D007150:Immunohistochemistry; D008954:Models, Biological; D010306:Parotid Gland / Q000378:metabolism*; D053499:Plasma Membrane Calcium-Transporting ATPases / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D064030:S100 Calcium Binding Protein G / Q000096:biosynthesis; D012463:Saliva / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases / Q000096:biosynthesis; D013363:Submandibular Gland / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000096:biosynthesis
C576764:CALB2 protein, human; D064032:Calbindin 2; D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D064030:S100 Calcium Binding Protein G; D050916:TRPV Cation Channels; C422827:TRPV6 protein, human; D053499:Plasma Membrane Calcium-Transporting ATPases; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; C506946:ATP2A2 protein, human; C506949:ATP2A3 protein, human; D002118:Calcium