A Specific Mechanomodulatory Role for p38 MAPK in Embryonic Joint Articular Surface Cell MEK-ERK Pathway Regulation

Abstract

Mechanisms regulating cell behavior and extracellular matrix composition in response to mechanical stimuli remain unresolved. Our previous studies have established that the MEK-ERK cascade plays a specific role in the mechano-dependent joint formation process by promoting the assembly of pericellular matrices reliant upon hyaluronan (HA) for their integrity. Here we demonstrate: (i) novel cross-talk between p38 MAPK and MEK-ERK signaling pathways that is specific for mechanical stimuli and (ii) a role for p38 MAPK in facilitating HA production by cells derived from the articular surface of embryonic chick tibiotarsal joints. We find that p38 MAPK blockade restricts pericellular assembly of HA-rich matrices and reduces basal as well as mechanical strain-induced release of HA. p38 MAPK blockers potentiated early strain-induced increases but restricted sustained increases in MEK/ERK phosphorylation at later times; c-Fos hyperphosphorylation at threonine 325 was found to parallel this p38 MAPK-mediated modulation of ERK activation. In contrast, p38 MAPK inhibitors had no detectable effect on the ERK activation induced by fibroblast growth factor 2 or pervanadate, a phosphatase inhibitor, and MEK inhibitors did not influence p38 MAPK phosphorylation, confirming both the specificity and unidirectionality of p38 MAPK-ERK cross-talk. Immunochemical and immunoblotting studies revealed constitutive p38 MAPK activation in cells at, or derived from, developing articular joint surfaces. Unlike the MEK-ERK pathway, however, p38 MAPK was not further stimulated by mechanical stimulation in vitro. Thus, p38 MAPK specifically facilitates ERK activation and downstream signaling in response to mechanical stimuli. These results suggest that constitutively active p38 MAPK serves an essential, permissive role in mechanically induced changes in ERK activation and in the accumulation of HA-rich extracellular matrices that serve a key role in joint development.Mitogen-activated protein kinases (MAPKs) 3 are ubiquitous serine/ threonine kinases that are activated by diverse extracellular stimuli, including growth factors, cytokines, and physiological mechanical signals (1-3). MAPKs are essential for transducing signals from the cell surface that regulate diverse cellular behaviors, such as those coordinating development, proliferation, and differentiation. Much recent emphasis has been placed on members of three well characterized mammalian MAPK families, comprising extracellular signal-regulated kinases (ERKs), p38 MAPKs, and c-Jun N-terminal kinases (JNKs) (4 -6). Until relatively recently it was considered that these families were preferentially activated by certain types of signal: the ERK family by growth factors and the p38 MAPK and JNK families by cellular stress. It is now becoming increasingly clear, however, that the various MAPK pathways can also be co-activated by a single stimulus. The precise interaction between members of these distinct MAPK families and how they cooperate to control cell behavior are, however, ill-define...

Cell Density–Dependent Increase of Constitutive Signal Transducers and Activators of Transcription 3 Activity in Melanoma Cells Is Mediated by Janus Kinases

“…4), common for melanoma cells (1,37). This was efficiently prevented by blocking MAPK/ERK kinase 1/2 (U0126) and surprisingly by inhibition of p38, implying a possible cross-talk between p38 and ERK in response to, for example, mechanical stress as has recently been reported (23,38,39). As expected, phosphorylation of ERK1/2 was influenced neither by the JAK nor by the Src inhibitors.…”

Stretch‐induced activation of ERK in myocytes is p38 and calcineurin‐dependent

“…A recent study in AS cells has shown that inhibition of p38-activation by the antagonist SB203580 inhibits activation of ERK in response to a mechanical stimulus. 5 In contrast, inhibition of the MEK/ERK pathway had no effect upon the activation of p38. We have therefore also examined in this study the effects of inhibiting the p38 pathway upon the levels of ERK activation in response to a mechanical stimulus.…”

“…3 In both cardiac myocytes and cells derived from the joint articular surface (AS) there is now a considerable body of evidence that signalling pathways involving the mitogen-activated protein kinases (MAPKs) are crucial to mediating the responses to mechanical stimuli. 4,5 In particular it has been demonstrated that both p38 and extracellular regulated kinase (ERK) pathways can be co-activated in response to a mechanical stimulus and that physiological responses may involve cross-talk between these different pathways. 5 The role that these different MAPK pathways play both singly and in combination on the regulation of mechanically induced alterations in skeletal muscle phenotype is unclear.…”

“…4,5 In particular it has been demonstrated that both p38 and extracellular regulated kinase (ERK) pathways can be co-activated in response to a mechanical stimulus and that physiological responses may involve cross-talk between these different pathways. 5 The role that these different MAPK pathways play both singly and in combination on the regulation of mechanically induced alterations in skeletal muscle phenotype is unclear.…”

Promotion of Cancer Cell Migration

“…One explanation is that constitutive ERK1/2 activation in these cells is necessary but not sufficient for IGFBP-6-dependent migration as has been suggested previously for H-ras-induced migration (49). Constitutive ERK1/2 activation may result in downstream cross-talk with IGFBP-6-induced p38 MAPK activation thereby resulting in the migration response (52)(53)(54)(55). Alternatively, MAPK kinase may also activate kinases other than ERK1/2 and mediate alternative signaling pathways (56,57).…”