ADAM12 induces actin cytoskeleton and extracellular matrix reorganization during early adipocyte differentiation by regulating beta1 integrin function.
Changes in cell shape are a morphological hallmark of differentiation. In this study we report that the expression of ADAM12, a disintegrin and metalloprotease, dramatically affects cell morphology in preadipocytes, changing them from a flattened, fibroblastic appearance to a more rounded shape. We showed that the highest levels of ADAM12 mRNA were detected in preadipocytes at the critical stage when preadipocytes become permissive for adipogenic differentiation. Furthermore, as assessed by immunostaining, ADAM12 was transiently expressed at the cell surface concomitant with the reduced activity of beta1 integrin. Co-immunoprecipitation studies indicated the formation of ADAM12/beta1 integrin complexes in these preadipocytes. Overexpression of ADAM12 at the cell surface of 3T3-L1 preadipocytes achieved by transient transfection or retroviral transduction led to the disappearance of the extensive network of actin stress fibers that are characteristic of these cells, and its reorganization into a cortical network located beneath the cell membrane. The cells became more rounded, exhibited fewer vinculin-positive focal adhesions, and adhered less efficiently to fibronectin in attachment assays. Moreover, ADAM12-expressing cells were more prone to apoptosis, which could be prevented by treating the cells with beta1-activating antibodies. A reduced and re-organized fibronectin-rich extracellular matrix accompanied these changes. In addition, beta1 integrin was more readily extracted with Triton X-100 from cells overexpressing ADAM12 than from control cells. Collectively, these results show that surface expression of ADAM12 impairs the function of beta1 integrins and, consequently, alters the organization of the actin cytoskeleton and extracellular matrix. These events may be necessary for early adipocyte differentiation.
Kawaguchi
Nobuko
N
Institute of Molecular Pathology, University of Copenhagen, Frederik V's vej 11, 2100 Copenhagen, Denmark.
Sundberg
Christina
C
Kveiborg
Marie
M
Moghadaszadeh
Behzad
B
Asmar
Meena
M
Dietrich
Nikolaj
N
Thodeti
Charles K
CK
Nielsen
Finn C
FC
Möller
Peter
P
Mercurio
Arthur M
AM
Albrechtsen
Reidar
R
Wewer
Ulla M
UM
D051722:ADAM Proteins; D000072199:ADAM12 Protein; D000199:Actins / Q000378:metabolism*; D017667:Adipocytes / Q000378:metabolism*; D000818:Animals; D002448:Cell Adhesion; D002454:Cell Differentiation; D048429:Cell Size; D002478:Cells, Cultured; D003001:Cloning, Molecular; D006224:Cricetinae; D003412:Cricetulus; D003599:Cytoskeleton / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008666:Metalloendopeptidases / Q000378:metabolism*; D051379:Mice; D017830:Octoxynol / Q000378:metabolism; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000494:pharmacology; D012190:Retroviridae; D022502:Stress Fibers / Q000378:metabolism
D000199:Actins; D005353:Fibronectins; D019012:Integrin beta1; D008565:Membrane Proteins; D034741:RNA, Small Interfering; D017830:Octoxynol; D051722:ADAM Proteins; D000072199:ADAM12 Protein; C000606480:ADAM12 protein, human; D008666:Metalloendopeptidases