Expression of the proteoglycan syndecan-4 and the mechanism by which it mediates stress fiber formation in folliculostellate cells in the rat anterior pituitary gland.
Folliculostellate (FS) cells in the anterior pituitary gland appear to have multifunctional properties. FS cells connect to each other at gap junctions and thereby form a histological and functional network. We have performed a series of studies on network formation in FS cells and recently reported that FS cells markedly prolong their cytoplasmic processes and form numerous interconnections with neighboring FS cells in the presence of laminin, an extracellular matrix (ECM) component of the basement membrane. In this study, we investigated the mechanism of this extension of FS cell cytoplasmic processes under the influence of laminin and found that laminin promoted stress fiber formation within FS cells. Next, we noted that formation of stress fibers in FS cells was mediated by syndecan-4, a transmembrane proteoglycan that binds ECM and soluble factors via their extracellular glycosaminoglycan chain. We then observed that expressions of syndecan-4 and α-actinin (a microfilament bundling protein that cross-links actin stress fibers in FS cells) were upregulated by laminin. Using specific siRNA of syndecan-4, actin polymerization of FS cells was inhibited. Our findings suggest that FS cells received a signal from laminin-syndecan-4 interaction, which resulted in morphological changes, and that the formation of a morphological and functional network in FS cells was transduced by a syndecan-4-dependent mechanism in the presence of ECM.
Division of Histology and Cell Biology, Department of Anatomy, Jichi Medical University School of Medicine, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan. kota@jichi.ac.jp
Kotaro
K
Horiguchi
Tom
T
Kouki
Ken
K
Fujiwara
Takehiro
T
Tsukada
Floren
F
Ly
Motoshi
M
Kikuchi
Takashi
T
Yashiro
D000818:Animals; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D005786:Gene Expression Regulation / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000235:genetics; D007797:Laminin / Q000378:metabolism; D008297:Male; D009414:Nerve Growth Factors / Q000235:genetics; D010903:Pituitary Gland, Anterior / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D011485:Protein Binding / Q000187:drug effects; D011509:Proteoglycans / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D055647:Rats, Transgenic; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D022502:Stress Fibers / Q000235:genetics / Q000378:metabolism*; D053671:Syndecan-4 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism
D007797:Laminin; D009414:Nerve Growth Factors; D011509:Proteoglycans; D034741:RNA, Small Interfering; D064568:S100 Calcium Binding Protein beta Subunit; D009418:S100 Proteins; C508307:Sdc4 protein, rat; D053671:Syndecan-4; D049452:Green Fluorescent Proteins