Biology subjects

de Assis Lima, M.

Publications and source records attributed to de Assis Lima, M..

2 recordsLinked to original sources

bioRxiv2026

A genetically encoded RhoG FRET biosensor reveals spatially compartmentalized RhoG-Rac1 signaling during cell protrusion

RhoG is a member of the Rho-family of small GTPases, and is closely related to the canonical Rac1 GTPase, implicated in membrane trafficking, dorsal ruffling, macropinocytosis, and cell protrusion, but its activity has been difficult to visualize directly in living cells with high spatial and temporal resolution. Here, we developed and validated a genetically encoded, single-chain Forster resonance energy transfer (FRET) biosensor for RhoG based on a C-terminal full-length RhoG and an intramolecular RhoG-binding domain derived from ELMO1. The biosensor showed a robust dynamic range when comparing constitutively active and inactive RhoG mutants, responded appropriately to regulation by RhoGDI, GAPs, and GEFs, and detected growth factor-stimulated RhoG activation in live cells. Imaging in mouse embryonic fibroblasts revealed dynamic RhoG activation at leading-edge protrusions, dorsal ruffles, and forming pinocytic and macropinocytic structures. To define the signaling relationship between RhoG and its closely related family member Rac1, we combined the RhoG biosensor with a near-infrared Rac1 FRET biosensor for simultaneous live-cell imaging. Morphodynamic mapping showed that both RhoG and Rac1 activities were positively coupled to edge protrusion, with strongest correlations near the leading-edge, but their direct coupling varied with distance from the edge, indicating partial spatial decoupling within protrusive regions. Inhibition of Src-family kinases altered RhoG dynamics, strongly suppressed Rac1 coupling to protrusion, and inverted the normal positive correlation between RhoG and Rac1 activities. Signaling microdomain analysis further showed that Src inhibition selectively prolonged Rac1 microdomain lifetimes without significantly affecting RhoG domains. Together, these results establish a new biosensor for direct visualization of RhoG activity and reveal that RhoG and Rac1 are coordinated but spatially and temporally distinct components of protrusion-associated signaling networks, with Src-family kinases playing a central role in maintaining their normal coupling.

cell biology↗

bioRxiv2026

Sensory neurons inhibit invadopodia and metastasis via direct CGRP-RAMP1-cAMP signaling to cancer cells

Breast cancer is globally the most common cancer among women. Although the five-year survival rate exceeds 80% for patients with localized disease, it drops to approximately 30% once metastasis occurs, underscoring the urgent need to define mechanisms that drive metastatic progression. Breast is a highly innervated organ and most of its innervation is sensory. However, whether sensory neurons can directly impact breast cancer cells remains an understudied topic. Here, we show that mammary tumors have increased CGRP sensory innervation. Using our novel microfluidic Device for Cancer cell-Axon Interaction Testing (DACIT), we demonstrate that the presence of axons strongly inhibits ECM-degrading ability of cancer cells. The sensory neuron secretome suppresses assembly and function of invadopodia, which are cancer cell protrusions controlling ECM degradation, and essential for intravasation and metastasis. We identify calcitonin gene-related peptide (CGRP) as the key component of the sensory neuron secretome responsible for the inhibitory effect. CGRP signaling occurs through the CRLR/RAMP1 receptor complex expressed by breast cancer cells, inducing a rapid increase in intracellular cAMP levels in breast cancer cells, followed by an increase in RhoC activity and suppression of invadopodia and ECM degradation. Loss of RAMP1 function enhances 3D spheroid invasion, cancer cell motility in vivo and significantly increases the number and the size of lung metastatic foci. Consistently, in silico analyses of both mouse and human RNASeq data point to a link between increasingly invasive subtypes with a gradual decrease in expression of RAMP1 and CRLR. To validate in silico findings, we compare RAMP1 expression in the patient breast tumors with adjacent normal tissues, confirming the invasive breast tumors have reduced levels of RAMP1. Together, our findings identify a protective role for the paracrine CGRP signaling in limiting breast cancer invasion and metastasis. We also demonstrate how cancer cells circumvent CGRP inhibition by suppressing RAMP1 expression, highlighting CGRP-RAMP1-cAMP axis as a potential therapeutic target in breast cancer.

cancer biology↗