Abstract:
Caveolae are omega-shaped structures that are found on eukaryotic plasma membranes
and enriched in sphingolipids and sterols. Caveolae act as membrane reservoirs to buffer
against changes in membrane tension, possibly explaining their abundance in cells
experiencing mechanical stress. Caveolin-1 (Cav-1) is an important structural component
of caveolae that is phosphorylated on its tyrosine-14. Cav-1 phosphorylation has also
been shown to regulate its mechanotransductory properties and focal adhesion tension.
In this study, we wanted to determine how WT MEFs respond to changing matrix
stiffness in 2D and 3D microenvironments of different matrix stiffness and the role of
Cav-1 and its Y14 phosphorylation in mediating this response. Our results show that in
WT MEFs seeded on collagen coated 2D polyacrylamide gels of increasing stiffness,
Cav-1 phosphorylation increases steadily. Adhesion dependent FAK, Akt and EGFR
activation also increase as stiffness increases. Upon loss of Cav-1, this stiffness
dependent activation of FAK, Akt and EGFR are all deregulated in cells on gels of
stiffness 0.5 kPa, 2.5 kPa and 23 kPa, but maintained on glass. On the other hand, the
response of WT MEFs embedded in 3D collagen gels to changing matrix stiffness is
different. This is reflected in their differential regulation of Cav-1 phosphorylation, FAK,
Akt and EGFR activation. Hence, Cav-1 and its phosphorylation could have different
roles in 2D and 3D microenvironments and this could contribute differentially to
regulating cellular function.
