Cytoskeletal disassembly and cell rounding promotes adipogenesis from ES cells.
Biomechanical signals such as cell shape and spreading play an important role in controlling stem cell commitment. Cell shape, adhesion and spreading are also affected by calreticulin, a multifunctional calcium-binding protein, which influences several cellular processes, including adipogenesis. Here we show that cytoskeletal disruption in mouse embryonic stem cells using cytochalasin D or nocodazole promotes adipogenesis. While cytochalasin D disrupts stress fibres and inhibits focal adhesion formation, nocodazole depolymerises microtubules and promotes focal adhesion formation. Furthermore, cytochalasin D increases the levels of both total and activated calcium/calmodulin-dependent protein kinase II, whereas nocodazole decreases it. Nevertheless, both treatments significantly increase the adipogenic potential of embryonic stem cells in vitro. Both cytochalasin D and nocodazole exposure caused cell rounding suggesting that it is cell shape that causes the switch towards the adipogenic programme. Calreticulin-containing embryonic stem cells, under baseline conditions, show low adipogenic potential, have low activity of signalling via calcium/calmodulin-dependent protein kinase II and display normal adhesive properties and cellular spreading in comparison to the highly adipogenic but poorly spread calreticulin-deficient ES cells. We conclude that forced cell rounding via cytoskeletal disruption overrides the effects of calreticulin, an ER chaperone, thus negatively regulating adipogenesis via focal adhesion-mediated cell spreading.
Department of Laboratory Medicine and Pathobiology, University of Toronto, 1 King's College Circle, Medical Sciences Building, room 6326, Toronto, ON, M5S 1A8, Canada.
Tianshu
T
Feng
Eva
E
Szabo
Ewa
E
Dziak
Michal
M
Opas
D008841:Actin Cytoskeleton / Q000378:metabolism; D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D050156:Adipogenesis / Q000187:drug effects; D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2 / Q000378:metabolism; D002147:Calmodulin / Q000378:metabolism; D037282:Calreticulin / Q000378:metabolism; D002460:Cell Line; D048430:Cell Shape / Q000187:drug effects; D015638:Cytochalasin D / Q000494:pharmacology; D003599:Cytoskeleton / Q000187:drug effects / Q000378:metabolism*; D053595:Embryonic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D022001:Focal Adhesions / Q000378:metabolism; D040542:Mechanotransduction, Cellular; D051379:Mice; D008870:Microtubules / Q000378:metabolism; D015739:Nocodazole / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D050257:Tubulin Modulators / Q000494:pharmacology; D019061:src-Family Kinases
D002147:Calmodulin; D037282:Calreticulin; D050257:Tubulin Modulators; D015638:Cytochalasin D; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D015739:Nocodazole