scholarly journals Quantitative Changes in Integrin and Focal Adhesion Signaling Regulate Myoblast Cell Cycle Withdrawal

1999 ◽  
Vol 144 (6) ◽  
pp. 1295-1309 ◽  
Author(s):  
Sarita K. Sastry ◽  
Margot Lakonishok ◽  
Stanley Wu ◽  
Tho Q. Truong ◽  
Anna Huttenlocher ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Map Kinase ◽  
Focal Adhesion ◽  
Ectopic Expression ◽  
Terminal Differentiation ◽  
Cytoplasmic Domain ◽  
Cytoplasmic Domains ◽  
Α Subunit ◽  
Kinase Activation ◽  
Quantitative Changes

We previously demonstrated contrasting roles for integrin α subunits and their cytoplasmic domains in controlling cell cycle withdrawal and the onset of terminal differentiation (Sastry, S., M. Lakonishok, D. Thomas, J. Muschler, and A.F. Horwitz. 1996. J. Cell Biol. 133:169–184). Ectopic expression of the integrin α5 or α6A subunit in primary quail myoblasts either decreases or enhances the probability of cell cycle withdrawal, respectively. In this study, we addressed the mechanisms by which changes in integrin α subunit ratios regulate this decision. Ectopic expression of truncated α5 or α6A indicate that the α5 cytoplasmic domain is permissive for the proliferative pathway whereas the COOH-terminal 11 amino acids of α6A cytoplasmic domain inhibit proliferation and promote differentiation. The α5 and α6A cytoplasmic domains do not appear to initiate these signals directly, but instead regulate β1 signaling. Ectopically expressed IL2R-α5 or IL2R-α6A have no detectable effect on the myoblast phenotype. However, ectopic expression of the β1A integrin subunit or IL2R-β1A, autonomously inhibits differentiation and maintains a proliferative state. Perturbing α5 or α6A ratios also significantly affects activation of β1 integrin signaling pathways. Ectopic α5 expression enhances expression and activation of paxillin as well as mitogen-activated protein (MAP) kinase with little effect on focal adhesion kinase (FAK). In contrast, ectopic α6A expression suppresses FAK and MAP kinase activation with a lesser effect on paxillin. Ectopic expression of wild-type and mutant forms of FAK, paxillin, and MAP/erk kinase (MEK) confirm these correlations. These data demonstrate that (a) proliferative signaling (i.e., inhibition of cell cycle withdrawal and the onset of terminal differentiation) occurs through the β1A subunit and is modulated by the α subunit cytoplasmic domains; (b) perturbing α subunit ratios alters paxillin expression and phosphorylation and FAK and MAP kinase activation; (c) quantitative changes in the level of adhesive signaling through integrins and focal adhesion components regulate the decision of myoblasts to withdraw from the cell cycle, in part via MAP kinase.

scholarly journals Chromatin organization changes during the establishment and maintenance of the postmitotic state

2017 ◽  
Author(s):  
Yiqin Ma ◽  
Laura Buttitta
Keyword(s):  
Cell Cycle ◽  
Gene Silencing ◽  
Ectopic Expression ◽  
Terminal Differentiation ◽  
Chromatin Organization ◽  
Cell Cycle Exit ◽  
Heterochromatin Protein 1 ◽  
Developmental Potential ◽  
Close Relationship ◽  
The Face

SummaryBackgroundGenome organization changes during development as cells differentiate. Chromatin motion becomes increasingly constrained and heterochromatin clusters as cells become restricted in their developmental potential. These changes coincide with slowing of the cell cycle, which can also influence chromatin organization and dynamics. Terminal differentiation is often coupled with permanent exit from the cell cycle and existing data suggests a close relationship between a repressive chromatin structure and silencing of the cell cycle in postmitotic cells. Here we examine the relationship between chromatin organization, terminal differentiation and cell cycle exit.ResultsWe focused our studies on the Drosophila wing, where epithelial cells transition from active proliferation to a postmitotic state in a temporally controlled manner. We find there are two stages of G0 in this tissue, a flexible G0 period where cells can be induced to re-enter the cell cycle under specific genetic manipulations and a state we call “robust”, where cells become strongly refractory to cell cycle re-entry. Compromising the flexible G0 by driving ectopic expression of cell cycle activators causes a global disruption of the clustering of heterochromatin-associated histone modifications such as H3K27 trimethylation and H3K9 trimethylation, as well as their associated repressors, Polycomb and heterochromatin protein 1(HP1). However, this disruption is reversible. When cells enter a robust G0 state, even in the presence of ectopic cell cycle activity, clustering of heterochromatin associated modifications are restored. If cell cycle exit is bypassed, cells in the wing continue to terminally differentiate, but heterochromatin clustering is severely disrupted. Heterochromatin-dependent gene silencing does not appear to be required for cell cycle exit, as compromising the H3K27 methyltransferase Enhancer of zeste, and/or HP1 cannot prevent the robust cell cycle exit, even in the face of normally oncogenic cell cycle activities.ConclusionsHeterochromatin clustering during terminal differentiation is a consequence of cell cycle exit, rather than differentiation. Compromising heterochromatin-dependent gene silencing does not disrupt cell cycle exit.

Cell heterogeneity upon myogenic differentiation: down-regulation of MyoD and Myf-5 generates ‘reserve cells’

1998 ◽  
Vol 111 (6) ◽  
pp. 769-779 ◽  
Author(s):  
N. Yoshida ◽  
S. Yoshida ◽  
K. Koishi ◽  
K. Masuda ◽  
Y. Nabeshima
Keyword(s):  
Cell Cycle ◽  
Myogenic Differentiation ◽  
Significant Proportion ◽  
Ectopic Expression ◽  
Terminal Differentiation ◽  
Growth Conditions ◽  
Down Regulation ◽  
Undifferentiated Cells ◽  
Myoblast Cells ◽  
Myod Expression

When a proliferating myoblast culture is induced to differentiate by deprivation of serum in the medium, a significant proportion of cells escape from terminal differentiation, while the rest of the cells differentiate. Using C2C12 mouse myoblast cells, this heterogeneity observed upon differentiation was investigated with an emphasis on the myogenic regulatory factors. The differentiating part of the cell population followed a series of well-described events, including expression of myogenin, p21(WAF1), and contractile proteins, permanent withdrawal from the cell cycle and cell fusion, whereas the rest of the cells did not initiate any of these events. Interestingly, the latter cells showed an undetectable or greatly reduced level of MyoD and Myf-5 expression, which had been originally expressed in the undifferentiated proliferating myoblasts. When these undifferentiated cells were isolated and returned to the growth conditions, they progressed through the cell cycle and regained MyoD expression. These cells demonstrated identical features with the original culture on the deprivation of serum. They produced both MyoD-positive differentiating and MyoD-negative undifferentiated populations once again. Thus the undifferentiated cells in the serum-deprived culture were designated ‘reserve cells’. Upon serum deprivation, MyoD expression rapidly decreased as a result of down-regulation in approximately 50% of the cells. After this heterogenization, MyoD positive cells expressed myogenin, which is the earliest known event of terminal differentiation and marks irreversible commitment to this, while MyoD-negative cells did not differentiate and became the reserve cells. We also demonstrated that ectopic expression of MyoD converted the reserve cells to differentiating cells, indicating that down-regulation of MyoD is a causal event in the formation of reserve cells.

scholarly journals Shc and Fak Differentially Regulate Cell Motility and Directionality Modulated by Pten

1999 ◽  
Vol 146 (2) ◽  
pp. 389-404 ◽  
Author(s):  
Jianguo Gu ◽  
Masahito Tamura ◽  
Roumen Pankov ◽  
Erik H.J. Danen ◽  
Takahisa Takino ◽  
...  
Keyword(s):  
Cell Migration ◽  
Tumor Suppressor ◽  
Cell Motility ◽  
Map Kinase ◽  
Focal Adhesion ◽  
Focal Adhesions ◽  
Dominant Negative ◽  
Kinase Activation ◽  
Protein Map ◽  
Mitogen Activated Protein

Cell migration is modulated by regulatory molecules such as growth factors, oncogenes, and the tumor suppressor PTEN. We previously described inhibition of cell migration by PTEN and restoration of motility by focal adhesion kinase (FAK) and p130 Crk-associated substrate (p130Cas). We now report a novel pathway regulating random cell motility involving Shc and mitogen-activated protein (MAP) kinase, which is downmodulated by PTEN and additive to a FAK pathway regulating directional migration. Overexpression of Shc or constitutively activated MEK1 in PTEN- reconstituted U87-MG cells stimulated integrin- mediated MAP kinase activation and cell migration. Conversely, overexpression of dominant negative Shc inhibited cell migration; Akt appeared uninvolved. PTEN directly dephosphorylated Shc. The migration induced by FAK or p130Cas was directionally persistent and involved extensive organization of actin microfilaments and focal adhesions. In contrast, Shc or MEK1 induced a random type of motility associated with less actin cytoskeletal and focal adhesion organization. These results identify two distinct, additive pathways regulating cell migration that are downregulated by tumor suppressor PTEN: one involves Shc, a MAP kinase pathway, and random migration, whereas the other involves FAK, p130Cas, more extensive actin cytoskeletal organization, focal contacts, and directionally persistent cell motility. Integration of these pathways provides an intracellular mechanism for regulating the speed and the directionality of cell migration.

Microtubule and chromatin behavior follow MAP kinase activity but not MPF activity during meiosis in mouse oocytes

Development ◽  
1994 ◽  
Vol 120 (4) ◽  
pp. 1017-1025 ◽  
Author(s):  
M.H. Verlhac ◽  
J.Z. Kubiak ◽  
H.J. Clarke ◽  
B. Maro
Keyword(s):  
Cell Cycle ◽  
Myelin Basic Protein ◽  
Map Kinase ◽  
Kinase Activity ◽  
Basic Protein ◽  
Chromatin Condensation ◽  
Meiotic Maturation ◽  
Protein Kinase Activity ◽  
Microtubule Organization ◽  
Kinase Activation

Oocyte meiotic maturation is triggered by different stimuli (hormones, unknown signals through cell interactions) in different species. These stimuli indirectly lead to the activation of a major cell cycle regulating activity, the maturation promoting factor (MPF). Other factors, such as the product of the proto-oncogene c-mos or enzymes of the MAP kinase family, are also involved in the process of maturation. MAP kinase activation occurs during meiotic maturation in oocytes from different species with different kinetics. The relationships between MPF activation and MAP kinase activation have been well studied in species such as clam and Xenopus. In this paper, we study the precise timing of MAP kinase activation (as measured by phosphorylation of exogenous myelin basic protein and shifts in mobility of ERK 1 and ERK 2) versus MPF activation (as measured by phosphorylation of exogenous histone H1) during mouse oocyte maturation and, in parallel, morphological events such as changes in microtubule organization and chromatin condensation. We observed that MAP kinase activation was delayed after MPF activation and that this activity persisted throughout maturation whereas MPF activity dropped between the two meiotic metaphases. After parthenogenetic activation of ovulated eggs, MAP kinase inactivation was very slow compared to MPF inactivation. During the first mitotic cell cycle, a rise in myelin basic protein kinase activity at M-phase was observed but it was not related to MAP kinase activation. Furthermore, microtubules and chromatin remained in a metaphase-like state during the complete period of maturation (including the period between the two meiotic metaphases) and a few hours after activation.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Multiple requirements for SHPTP2 in epidermal growth factor-mediated cell cycle progression.

1996 ◽  
Vol 16 (3) ◽  
pp. 1189-1202 ◽  
Author(s):  
A M Bennett ◽  
S F Hausdorff ◽  
A M O'Reilly ◽  
R M Freeman ◽  
B G Neel
Keyword(s):  
Cell Cycle ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Map Kinase ◽  
S Phase ◽  
Immediate Early ◽  
Kinase Activation ◽  
Epidermal Growth ◽  
Tyrosyl Phosphorylation ◽  
Phase Entry

Using transient overexpression and microinjection approaches, we examined SHPTP2's function in growth factor signaling. Overexpression of catalytically inactive SHPTP2 (PTP2CS) but not catalytically inactive SHPTP1, inhibited mitogen-activated protein (MAP) kinase activation and Elk-1 transactivation following epidermal growth factor (EGF) stimulation of 293 cells. An SHPTP2 mutant with both C-terminal tyrosyl phosphorylation sites converted to phenylalanine (PTP2YF) was also without effect; moreover, PTP2YF rescued PTP2CS-induced inhibition of EGF-induced Elk-1 transactivation. PTP2CS did not inhibit transactivation by activated Ras, suggesting that SHPTP2 acts upstream of or parallel to Ras. Neither PTP2CS nor PTP2YF inhibited platelet-derived growth factor (PDGF)-induced Elk-1 transactivation. Thus, protein-tyrosine phosphatase activity, but not tyrosyl phosphorylation of SHPTP2, is required for the immediate-early responses to EGF but not to PDGF. To determine whether SHPTP2 is required later in the cell cycle, we assessed S-phase entry in NIH 3T3 cells microinjected with anti-SHPTP2 antibodies or with a glutathione S-transferase (GST) fusion protein encoding both SH2 domains (GST-SH2). Microinjection of anti-SHPTP2 antibodies prior to stimulation inhibited EGF- but no PDGF- or serum-induced S-phase entry. Anti-SHPTP2 antibodies or GST-SH2 fusion protein could inhibit EGF-induced S-phase entry for up to 8 h after EGF addition. Although MAP kinase activation was detected shortly after EGF stimulation, no MAP kinase activation was detected around the restriction point. Therefore, SHPTP2 is absolutely required for immediate-early and late events induced by some, but not all, growth factors, and the immediate-early and late signal transduction pathways regulated by SHPTP2 are distinguishable.

scholarly journals Contrasting roles for integrin beta 1 and beta 5 cytoplasmic domains in subcellular localization, cell proliferation, and cell migration.

1994 ◽  
Vol 125 (2) ◽  
pp. 447-460 ◽  
Author(s):  
R Pasqualini ◽  
M E Hemler
Keyword(s):  
Cell Proliferation ◽  
Cell Migration ◽  
Focal Adhesion ◽  
Cho Cells ◽  
Detailed Comparison ◽  
Cytoplasmic Domain ◽  
Integrin Subunit ◽  
Cytoplasmic Domains ◽  
Migration Assay ◽  
Inside Out

To carry out a detailed comparison of the roles of integrin beta 1 and beta 5 cytoplasmic domains, we expressed both wild type beta 1 and chimeric beta 1/5 constructs in CHO cells. In the latter, the cytoplasmic domain of beta 1 was replaced with that of beta 5. The human beta 1 and beta 1/5 constructs appeared at similar levels at the cell surface (mostly as alpha 5 beta 1 heterodimers) and contributed equally to CHO cell adhesion to fibronectin. However, beta 1 but not beta 1/5 localized to focal adhesion-like structures when CHO cells were spread on fibronectin. Furthermore, only the beta 1-CHO cells showed increased proliferation in response to fibronectin plus an integrin-activating anti-beta 1 antibody, and showed increased appearance of 32P-labeled protein (p90) that correlated with proliferation. In sharp contrast, the beta 1/5-CHO cells were notably more migratory than beta 1-CHO cells in a transwell haptotactic migration assay. These results indicate that the beta 1 and beta 5 integrin subunit cytoplasmic domains can translate similar adhesive information into highly contrasting subsequent events. Thus, we have established that "inside-out" and "outside-in" integrin signaling pathways are regulated by fundamentally distinct mechanisms. In addition, we suggest that the same properties of the beta 1 cytoplasmic domain that promote recruitment to visible focal adhesion-like structures may also be conductive to cell proliferation. Conversely, the properties of the beta 5 tail that make it less likely to localize into focal adhesion-like structures may contribute to enhanced cell migration.

scholarly journals R-Ras Signals through Specific Integrin α Cytoplasmic Domains to Promote Migration and Invasion of Breast Epithelial Cells

1999 ◽  
Vol 145 (5) ◽  
pp. 1077-1088 ◽  
Author(s):  
Patricia J. Keely ◽  
Elena V. Rusyn ◽  
Adrienne D. Cox ◽  
Leslie V. Parise
Keyword(s):  
Epithelial Cells ◽  
Signaling Pathways ◽  
Cytoplasmic Domain ◽  
Cellular Adhesion ◽  
Limiting Factors ◽  
Migration And Invasion ◽  
Cytoplasmic Domains ◽  
Α Subunit ◽  
Breast Epithelial Cells ◽  
Breast Epithelial

Specificity and modulation of integrin function have important consequences for cellular responses to the extracellular matrix, including differentiation and transformation. The Ras-related GTPase, R-Ras, modulates integrin affinity, but little is known of the signaling pathways and biological functions downstream of R-Ras. Here we show that stable expression of activated R-Ras or the closely related TC21 (R-Ras 2) induced integrin-mediated migration and invasion of breast epithelial cells through collagen and disrupted differentiation into tubule structures, whereas dominant negative R-Ras had opposite effects. These results imply novel roles for R-Ras and TC21 in promoting a transformed phenotype and in the basal migration and polarization of these cells. Importantly, R-Ras induced an increase in cellular adhesion and migration on collagen but not fibronectin, suggesting that R-Ras signals to specific integrins. This was further supported by experiments in which R-Ras enhanced the migration of cells expressing integrin chimeras containing the α2, but not the α5, cytoplasmic domain. In addition, a transdominant inhibition previously noted only between integrin β cytoplasmic domains was observed for the α2 cytoplasmic domain; α2β1-mediated migration was inhibited by the expression of excess α2 but not α5 cytoplasmic domain-containing chimeras, suggesting the existence of limiting factors that bind the integrin α subunit. Using pharmacological inhibitors, we found that R-Ras induced migration on collagen through a combination of phosphatidylinositol 3-kinase and protein kinase C, but not MAPK, which is distinct from the other Ras family members, Rac, Cdc42, and N- and K-Ras. Thus, R-Ras communicates with specific integrin α cytoplasmic domains through a unique combination of signaling pathways to promote cell migration and invasion.

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