Expression and localization of calpain 3 in the submandibular gland of mice.
OBJECTIVE
Calpains comprise a family of intracellular Ca2+-dependent cysteine proteases and are considered to play roles in various physiological phenomena with limited proteolytic activities against specific substrates. We herein revealed the expression and localization of calpain 3, the muscle-type calpain, in the submandibular gland (SMG) of mice.


METHODS
The expression of the mRNA for conventional, ubiquitous calpains 1 and 2 and skeletal muscle-specific calpain 3 was examined in the major salivary glands of mice using RT-PCR, and the expression and localization of calpain 3 protein was examined in the SMG of mice using immunohistochemistry and Western blotting.


RESULTS
The large catalytic subunits of calpains 1 and 2 and the small regulatory subunit common to calpains 1 and 2 were weakly expressed in the parotid gland, sublingual gland, and SMG at similar levels in males and females. In contrast, the single large catalytic subunit of calpain 3 was expressed predominantly in the SMG at markedly higher levels in males than in females and in a manner dependent on androgens. Immunoreactivity for calpain 3 was mainly localized in cells of the granular convoluted tubules (GCT) that developed preferentially in the male SMG. In GCT cells, calpain 3 immunoreactivity was localized predominantly in the cytosolic region and was absent in the secretory granules.


CONCLUSIONS
These results revealed that the GCT is the primary site of production of calpain 3 in the mouse SMG.
Department of Histology and Cell Biology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, 920-8640, Japan; Department of Anatomy, Faculty of Medical Science, Naresuan University, Pitsanulok, 65000, Thailand.
Tewarat
T
Kumchantuek
Department of Histology and Cell Biology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, 920-8640, Japan.
Hiroki
H
Nakata
Department of Histology and Cell Biology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, 920-8640, Japan; Department of Anatomy, Faculty of Medical Science, Naresuan University, Pitsanulok, 65000, Thailand.
Natthiya
N
Sakulsak
Department of Histology and Cell Biology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, 920-8640, Japan.
Miyuki
M
Yamamoto
Department of Histology and Cell Biology, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, 920-8640, Japan. Electronic address: siseki@med.kanazawa-u.ac.jp.
Shoichi
S
Iseki
D000728:Androgens / Q000378:metabolism; D000818:Animals; D000906:Antibodies; D015153:Blotting, Western; D002154:Calpain / Q000096:biosynthesis / Q000378:metabolism*; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009124:Muscle Proteins / Q000096:biosynthesis / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods; D012727:Sex Characteristics; D013361:Sublingual Gland / Q000378:metabolism; D013363:Submandibular Gland / Q000166:cytology / Q000000981:diagnostic imaging / Q000378:metabolism*
D000728:Androgens; D000906:Antibodies; D009124:Muscle Proteins; D012333:RNA, Messenger; D002154:Calpain; C491373:Capn3 protein, mouse; C112682:Capn1 protein, mouse; C570925:Capn2 protein, mouse
Calpain 3; Granular convoluted tubules; Mouse; Sexual dimorphism; Submandibular gland