DDR1 regulates the stabilization of cell surface E-cadherin and E-cadherin-mediated cell aggregation.
The stabilization of cell surface E-cadherin is important for the maintenance of apical junction complexes and epithelial polarity. Previously, we reported that discoidin domain receptor 1 (DDR1) forms a complex with E-cadherin at adhesive contacts; however, the regulatory role of DDR1 in the stabilization of cell surface E-cadherin and E-cadherin-mediated cell behaviors remained undefined. To gain insight into these questions, we utilized two stable clones depleted for DDR1 via the small interfering RNA (siRNA) technique, and we over-expressed DDR1 in MDCK cells. We performed Western blotting, immunofluorescence analysis, flow cytometry, and cell aggregation studies to investigate the effect of DDR1 on cell surface E-cadherin. The results showed that both DDR1/2 and E-cadherin use their extracellular domains to form DDR/E-cadherin complexes. Neither the depletion nor the over-expression of DDR1 changed the expression level of E-cadherin in MDCK cells. Collagen disrupted the formation of E-cadherin complexes and caused E-cadherin to accumulate in the cytoplasm; however, over-expression of DDR1 stabilized E-cadherin on the cell surface and decreased its cytoplasmic accumulation. Furthermore, independently of collagen stimulation, the depletion of DDR1 resulted in a decrease in the level of cell surface E-cadherin, which consequently caused its cytoplasmic accumulation and decreased E-cadherin-mediated cell aggregation. These results indicate that DDR1 can increase the stability of cell surface E-cadherin and promote MDCK cell aggregation, which may be mediated through the formation of DDR1/E-cadherin complexes. Overall, these findings have implications for the physiological roles of DDR1 in association with the maintenance of both the adhesion junction and epithelial polarity.
Eswaramoorthy
Rajalakshmanan
R
Orthopedic Research Center, Kaohsiung Medical University, Kaohsiung, Taiwan.
Wang
Chih-Kuang
CK
Chen
Wen-Cheng
WC
Tang
Ming-Jer
MJ
Ho
Mei-Ling
ML
Hwang
Chi-Ching
CC
Wang
Hui-Min
HM
Wang
Chau-Zen
CZ
D000818:Animals; D015703:Antigens, CD; D015820:Cadherins / Q000737:chemistry / Q000378:metabolism*; D002449:Cell Aggregation / Q000187:drug effects; D002460:Cell Line; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism*; D003094:Collagen / Q000494:pharmacology; D004285:Dogs; D004705:Endocytosis / Q000187:drug effects; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D011485:Protein Binding / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry / Q000378:metabolism*; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism
D015703:Antigens, CD; C513384:CDH1 protein, human; D015820:Cadherins; D034741:RNA, Small Interfering; D003094:Collagen; D020794:Receptor Protein-Tyrosine Kinases