Caveolin-1 Modulates Mechanotransduction Responses to Substrate Stiffness through Actin-Dependent Control of YAP

摘要

class="head no_bottom_margin" id="sec1title">IntroductionThe integral membrane protein Caveolin-1 (CAV1) engages in crosstalk with the actin cytoskeleton and connects directly to actin cables through the protein FLNA (, ). CAV1 controls focal adhesion stability, actin organization, and actomyosin contraction through RHO GTPases (, , ) and contributes to mechanosensing and adaptation in response to various mechanical stimuli, such as membrane stretching, shear stress, hypoosmotic shock, and cell detachment (, , ). However, current understanding remains limited regarding the mechanisms by which these phenomena are integrated with overall cell function.The transcriptional cofactor yes-associated protein (YAP) operates downstream of the canonical Hippo pathway (), a highly conserved pathway regulating organ growth control, tissue homeostasis, and tumorigenesis (). YAP regulates the transcription of specific gene sets mainly through its interaction with TEA domain (TEAD) transcription factors (). A cascade of kinases, including LATS1 and LATS2, lead to YAP phosphorylation and curb its nucleocytoplasmic shuttling, mediating its cytosolic retention through interaction with 14-3-3 proteins, thus downregulating YAP transcriptional output (, , ). This regulatory network is controlled by upstream cues related to tissue architecture and cellular context, such as cell-cell adhesion, cell density, and cell polarity (). YAP is also controlled by mechanical signals, such as extracellular matrix (ECM) stiffness, shear stress, and stretching (href="#bib11" rid="bib11" class=" bibr popnode">Codelia et al., 2014, href="#bib18" rid="bib18" class=" bibr popnode">Dupont et al., 2011, href="#bib68" rid="bib68" class=" bibr popnode">Zhong et al., 2013). Stiff environments favor YAP nuclear localization (i.e., activation), whereas attachment to soft substrates increases cytoplasmic retention. This mechanical control, which determines cell proliferation and differentiation (href="#bib18" rid="bib18" class=" bibr popnode">Dupont et al., 2011), depends on RHO GTPase function and actomyosin-driven contractility but is largely independent of kinase regulation, because (1) depletion of LATS1/2 kinases does not alter the mechanical responsiveness of YAP and (2) non-phosphorylatable mutants are nonetheless sensitive to substrate stiffness (href="#bib18" rid="bib18" class=" bibr popnode">Dupont et al., 2011, href="#bib20" rid="bib20" class=" bibr popnode">Elosegui-Artola et al., 2017). The adaptation of nuclear pore units to mechanical tension also contributes to the regulation of YAP nuclear entry (href="#bib20" rid="bib20" class=" bibr popnode">Elosegui-Artola et al., 2017). However, understanding is limited about the exact molecular mechanisms by which ECM stiffness controls YAP activity. Here, we identify CAV1 as an upstream positive regulator of YAP that affects the response to changes in ECM stiffness through a mechanism dependent on F-actin dynamics.The mechanical regulation of YAP underpins pathophysiological processes such as cardiovascular disease, inflammation and tissue regeneration, and cancer (href="#bib50" rid="bib50" class=" bibr popnode">Panciera et al., 2017). YAP activation by ECM stiffness promotes cancer-associated fibroblast activation and subsequent peritumoral ECM remodeling and stiffening, establishing a positive-feedback loop that favors cancer progression (href="#bib7" rid="bib7" class=" bibr popnode">Calvo et al., 2013). Here, we show that overexpression of constitutively active YAP mutants rescues the blunted contractility and ECM remodeling previously reported for Cav1 genetic deficiency (href="#bib24" rid="bib24" class=" bibr popnode">Goetz et al., 2011). The positive impact of YAP activity on tumor initiation and progression is further showcased by its critical contribution to pancreatitis-induced acinar-to-ductal metaplasia (ADM), which favors pancreatic ductal carcinoma (PDAC) initiation (href="#bib27" rid="bib27" class=" bibr popnode">Gruber et al., 2016). We further demonstrate CAV1-dependent positive regulation of YAP in vivo, showing that Cav1-knockout (Cav1KO) pancreatic parenchyma fails to upregulate YAP in response to induced pancreatitis and exhibits blunting of changes associated with YAP activation, such as ADM.Our results provide important insight into the mechanisms regulating YAP function. We identify CAV1 as an upstream regulator of YAP, controlling its transcriptional activity through the control of actin cytoskeleton dynamics. Conversely, YAP underpins an important share of CAV1-dependent phenotypes. We propose this CAV1-YAP regulation has important implications in the progression of some pathologies, such as cancer, and will allow us to better understand the principles governing processes driven by substrate stiffness in health and disease.