p27^Kip1Acts Downstream of N-Cadherin-mediated Cell Adhesion to Promote Myogenesis beyond Cell Cycle Regulation

Abstract

It is widely acknowledged that cultured myoblasts can not differentiate at very low density. Here we analyzed the mechanism through which cell density influences myogenic differentiation in vitro. By comparing the behavior of C2C12 myoblasts at opposite cell densities, we found that, when cells are sparse, failure to undergo terminal differentiation is independent from cell cycle control and reflects the lack of p27Kip1 and MyoD in proliferating myoblasts. We show that inhibition of p27Kip1 expression impairs C2C12 cell differentiation at high density, while exogenous p27Kip1 allows low-density cultured C2C12 cells to enter the differentiative program by regulating MyoD levels in undifferentiated myoblasts. We also demonstrate that the early induction of p27Kip1 is a critical step of the N-cadherin-dependent signaling involved in myogenesis. Overall, our data support an active role of p27Kip1 in the decision of myoblasts to commit to terminal differentiation, distinct from the regulation of cell proliferation, and identify a pathway that, reasonably, operates in vivo during myogenesis and might be part of the phenomenon known as "community effect".

Formation of E-Cadherin/β-Catenin–based Adherens Junctions in Hepatocytes Requires Serine-10 in p27(Kip1)

“…It is possible that additional adhesion proteins have compensated for the loss of E-cadherin and ␤-catenin at the cell surface, as was suggested in the conditional E-cadherin knockout mice (Battle et al, 2006). Regardless, the data in this study provide the first evidence that, in addition to the reported regulation of p27 expression in response to cell adhesion (Messina et al, 2005;Motti et al, 2005), p27 itself directly affects cell-cell adhesion via its Ser-10.…”

Actions of 1,25(OH)2-vitamin D3 on the cellular cycle depend on VDR and p38 MAPK in skeletal muscle cells

“…The induction of p27 Kip1 CKI is an early critical step of the N-cadherin-dependent signaling involved in myogenesis, showing an active role of p27 Kip1 CKI in the decision of myoblasts to undergo differentiation (Messina et al 2005). It is of relevance that when C2C12 myoblasts start expressing CKI, p21…”

“…cyclin D1 is highly expressed in proliferating cells and its expression is markedly reduced after 1 day on differentiation medium (Clemente et al 2005). With respect to CKIs, p21 Waf1/Cip1 plays an important role inhibiting the progression of the cellular cycle in C2C12 cells (Davidovic et al 2013), and an active role for p27 Kip1 at an early stage of differentiation has been established (Messina et al 2005). P38 MAPK (p38), a key signaling pathway involved in skeletal muscle differentiation, is a member of the MAPKs super family (Zetser et al 1999).…”

Common and specific roles of the related CDK inhibitors p27 and p57 revealed by a knock-in mouse model

“…Second, non-CKI functions of p27 and p57 may be important for developmental processes. Both p27 and p57 bind various molecules specifically (20 -27, 44), and contribute to certain developmental processes in a manner independent of their CKI activity (22,25,(45)(46)(47)(48). For example, stabilization of MyoD and inhibition of JNK by p57 promote myoblast differentiation (23,26,49), consistent with our finding that knocked-in p27 did not correct the abdominal muscle defect of p57 KO mice, despite its expression pattern being apparently identical to that of p57.…”