Biology subjects

Lopez-Sanchez, I.

Publications and source records attributed to Lopez-Sanchez, I..

5 recordsLinked to original sources

bioRxiv2021

GIV/Girdin, a Non-receptor Modulator for Gαi/s, Regulates Spatiotemporal Signaling during Sperm Capacitation and is Required for Male Fertility

For a sperm to successfully fertilize an egg, it must first undergo capacitation in the female reproductive tract, and later undergo acrosomal reaction (AR) upon encountering an egg surrounded by its vestment. How premature AR is avoided despite rapid surges in signaling cascades during capacitation remains unknown. Using a combination of KO mice and cell-penetrating peptides, we show that GIV (CCDC88A), a guanine nucleotide-exchange modulator (GEM) for trimeric GTPases, is highly expressed in spermatocytes and is required for male fertility. GIV is rapidly phosphoregulated on key tyrosine and serine residues in human and murine spermatozoa. These phosphomodifications enable GIV-GEM to orchestrate two distinct compartmentalized signaling programs in the sperm tail and head; in the tail, GIV enhances PI3K[->] Akt signals, sperm motility and survival, whereas in the head it inhibits cAMP surge and premature AR. Furthermore, GIV transcripts are downregulated in the testis and semen of infertile men. These findings exemplify the spatiotemporally segregated signaling programs that support sperm capacitation and shed light on a hitherto unforeseen cause of infertility in men. GRAPHIC ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=199 SRC="FIGDIR/small/442927v1_ufig1.gif" ALT="Figure 1"> View larger version (66K): org.highwire.dtl.DTLVardef@f4901forg.highwire.dtl.DTLVardef@2211dforg.highwire.dtl.DTLVardef@c37ff5org.highwire.dtl.DTLVardef@105eed7_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSO_LIGIV is highly expressed in spermatozoa, and is required for male fertility C_LIO_LIGIV is rapidly phosphoregulated during sperm capacitation C_LIO_LIIt enhances tyrosine-based signals in sperm tail, enhances motility C_LIO_LIIt suppresses cAMP in the sperm head, inhibits premature acrosome exocytosis C_LI

cell biology↗

bioRxiv2021

Closed-Loop Control between Two GTPase Switches makes the Secretory Functions of the Golgi Responsive to Growth Factors

Cancers represent complex autonomous systems, displaying self-sufficiency in growth signaling. Autonomous growth is fueled by a cancer cells ability to secrete-and-sense growth factors: a poorly understood phenomenon. Using an integrated systems and experimental approach, here we dissect the impact of a feedback-coupled GTPase circuit within the secretory pathway that imparts secretion-coupled autonomy. The circuit is assembled when the Ras-superfamily monomeric GTPase Arf1, and the heterotrimeric GTPase Gi{beta}{gamma} and their corresponding GAPs and GEFs are coupled by GIV/Girdin, a protein that is known to fuel aggressive traits in diverse cancers. One forward and two key negative feedback loops within the circuit create closed-loop control (CLC), allow the two GTPases to coregulate each other, and convert the expected switch-like behavior of Arf1-dependent secretion into an unexpected dose response alignment behavior of sensing and secretion. Such behavior translates into cell survival that is self-sustained by stimulus-proportionate secretion. Proteomic studies and protein-protein interaction network analyses pinpoint growth factors (e.g., the epidermal growth factor; EGF) as a key stimuli for such self-sustenance. Findings highlight how enhanced coupling of two biological switches in cancer cells is critical for multiscale feedback control to achieve secretion-coupled autonomy of growth factors. SYNOPSIS IMAGE O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY STANDFIRST TEXTThis work defines the inner workings of a Golgi-localized molecular circuitry comprised of coupled GTPases, which empowers cells to achieve self-sufficiency in growth factor signaling by creating a secrete-and-sense autocrine loop. HIGHLIGHTS/MAIN FINDINGSO_LIModeling and experimental approaches were used to dissect a coupled GTPase circuit. C_LIO_LICoupling enables closed loop feedback and mutual control of GTPases. C_LIO_LICoupling generates dose response alignment behavior of sensing and secretion of growth factors. C_LIO_LICoupling is critical for multiscale feedback control to achieve secretion-coupled autonomy. C_LI

systems biology↗

bioRxiv2020

Receptor tyrosine kinases activate heterotrimeric G proteins via phosphorylation within the interdomain cleft of Gαi

The molecular mechanisms by which receptor tyrosine kinases (RTKs) and heterotrimeric G proteins, two major signaling hubs in eukaryotes, independently relay signals across the plasma membrane have been extensively characterized. How these hubs crosstalk has been a long-standing question, but answers remain elusive. Using linear-ion-trap mass spectrometry in combination with biochemical, cellular, and computational approaches, we unravel a mechanism of activation of heterotrimeric G proteins by RTKs and chart the key steps that mediate such activation. Upon growth factor stimulation, the guanine-nucleotide exchange modulator, GIV, dissociates Gi*{beta}{gamma} trimers, scaffolds monomeric Gi with RTKs, and facilitates the phosphorylation on two tyrosines located within the inter-domain cleft of Gi. Phosphorylation triggers the activation of Gi and inhibits second messengers (cAMP). Tumor-associated mutants reveal how constitutive activation of this pathway impacts cells decision to go vs. grow. These insights define a tyrosine-based G protein signaling paradigm and reveal its importance in eukaryotes. Significance StatementGrowth factors and heterotrimeric G proteins are two of the most widely studied signaling pathways in eukaryotes; their crosstalk shapes some of the most fundamental cellular responses in both health and disease. Although mechanisms by which G protein pathways transactivate growth factor RTKs has been well-defined, how the reverse may happen is less understood. This study defines the key steps and cellular consequences of a fundamental mechanism of signal crosstalk that enables RTKs to transactivate heterotrimeric G protein, Gi. Mutations found in tumors shed light on how derailing this mechanism impacts tumor cell behavior. Thus, findings not only show how cells integrate extracellular signals via pathway crosstalk, but also demonstrate the relevance of this pathway in cancers.

biochemistry↗

bioRxiv2019

GIV-Kindlin interaction is required for Kindlin-Mediated Integrin Recognition and Activation

Cells perceive and respond to the extracellular matrix (ECM) via integrin receptors; their dysregulation has been implicated in inflammation and cancer metastasis. Here we show that a guanine nucleotide exchange modulator of trimeric-GTPase Gi, GIV (a.k.a Girdin), directly binds the integrin adaptor Kindlin-2. A non-canonical short linear motif within GIVs C-terminus binds Kindlin-2-FERM3 domain at a site that is distinct from the binding site for the canonical NPxY motif on the -integrin tail. Binding of GIV to Kindlin-2 allosterically enhances Kindlin-2s affinity for {beta}1-integrin. Consequently, integrin activation and clustering are maximized, which augments cell adhesion, spreading and invasion. Findings elucidate how the GIV*Kindlin-2 complex has a two-fold impact: it allosterically synergizes integrin activation and enables {beta}1-integrins to indirectly access and modulate trimeric GTPases via the complex. Furthermore, Cox proportional-hazard models on tumor transcriptomics provide trans-scale evidence of synergistic interactions between GIV*Kindlin-2*{beta}1-integrin on time to progression to metastasis. The eTOC blurbIntegrins mediate cell adhesion to the extracellular matrix; their dysregulation fuels inflammation, cancer cell invasion and metastasis. Authors show how two pro-metastatic scaffold proteins, Kindlin and GIV/Girdin bind and cooperatively enhance their allosteric coupling to integrins, and their subsequent activation. Findings reveal novel interfaces in integrin signaling for pharmacologic manipulation. HIGHLIGHTSO_LIGIV and Kindlin(K2), two integrin adaptors that promote metastasis, bind each other C_LIO_LIBinding of GIV or integrin to K2 allosterically enhances GIV*K2*integrin complexes C_LIO_LIBinding is required for the maximal recruitment of GIV and K2 to active integrins C_LIO_LIBinding facilitates integrin clustering, activation, tumor cell adhesion, invasion. C_LI

cell biology↗

bioRxiv2017

Convergence of Wnt, Growth Factor and Trimeric G protein signals on Daple

Cellular proliferation, differentiation, and morphogenesis are shaped by multiple signaling cascades; their concurrent dysregulation plays an integral role in cancer progression and is a common feature of many malignancies. Three such cascades that contribute to the oncogenic potential are the Wnt/Frizzled(FZD), growth factor-receptor tyrosine kinases (RTKs), and G-proteins/GPCRs. Here we identify Daple, a modulator of trimeric G-proteins and a Dishevelled (Dvl)-binding protein as an unexpected point of convergence for all three cascades. Daple-dependent activation of Gi and enhancement of non-canonical Wnt signals is not just triggered by Wnt5a/FZD to suppress tumorigenesis, but also hijacked by growth factor-RTKs to stoke tumor progression. Phosphorylation of Daple by both RTKs and non-RTKs triggers Gi activation and potentiates non-canonical Wnt signals that trigger epithelial-mesenchymal transition. In patients with colorectal cancers, concurrent upregulation of Daple and the prototype RTK, EGFR, carried poor prognosis. Thus, this work defines a novel growth factor{leftrightarrow}G-protein{leftrightarrow}Wnt crosstalk paradigm in cancer biology.

cancer biology↗