Biology subjects

McCollum, D.

Publications and source records attributed to McCollum, D..

5 recordsLinked to original sources

bioRxiv2025

Regulation of tension-dependent localization of LATS1 and LATS2 to adherens junctions.

The LIM domain protein LIMD1 is a critical regulator of the Hippo signaling pathway, acting to sequester the kinases LATS1/2 to adherens junctions (AJs) in response to mechanical strain. Here, we identify the molecular basis for LIMD1 binding and recruitment of LATS1/2 to AJs. We show that while the LIM domains of LIMD1 are sufficient for AJ localization and binding to LATS1/2, recruitment of LATS1 to AJ requires both the intrinsically disordered region (IDR) in the N-terminus as well as the LIM domains. We further dissected the LIM domains and found that LIM1 and LIM2, but not LIM3, are necessary for LATS1 AJ localization. Point mutations that disrupt strain sensitivity in either the first or second LIM domain disrupt both binding and recruitment of LATS1/2 to AJs. Mechanistically, LIMD1 binds LATS1/2 through a conserved linear motif, the LATS-LATCH, which we identified by AlphaFold modeling and confirmed by biochemical and localization assays. The LATS-LATCH is both necessary and sufficient for strain-dependent recruitment of LATS1/2 to AJs. Mutation of predicted contact residues within the LATS-LATCH both disrupts its binding to LIMD1 and localization to AJs. These findings define a bipartite mechanism for LIMD1-dependent recruitment of LATS1/2 involving LIM domain-LATCH interactions and N-terminal IDR functions, providing insight into how mechanical signals are transduced through the Hippo pathway.

cell biology↗

bioRxiv2025

Control of stress-activated Cdc42 dynamics by the MAP kinase Sty1-NDR kinase Orb6 regulatory axis

Cdc42 is a Rho-family GTPase that controls cell polarization from yeast to human cells. In fission yeast, under normal growth conditions, Cdc42-GTP oscillates between cell tips to promote polarized growth. However, when exposed to environmental stressors, Cdc42 adopts an "exploratory" pattern of Cdc42 activation along the cell membrane. This pattern also occurs when the NDR kinase Orb6 is downregulated. Here, we describe the molecular mechanism behind the emergence of exploratory Cdc42 dynamics and identify a new substrate of Orb6 kinase, the Cdc42 GAP Rga3. Additionally, we show that MAP kinase Sty1, known for linking stress signals to the Cdc42 polarity module, negatively regulates Orb6 kinase. During nutritional stress, activation of Sty1 and inactivation of Orb6 are associated with chronological lifespan extension. Our findings reveal a novel mechanism controlling cell morphology during stress, with important implications for cell survival.

cell biology↗

bioRxiv2023

The ability of the LIMD1 and TRIP6 LIM domains to bind to f-actin under strain is critical for their tension dependent localization to adherens junctions and association with the Hippo pathway kinase LATS1.

A key step in regulation of Hippo pathway signaling in response to mechanical tension is recruitment of the LIM domain proteins TRIP6 and LIMD1 to adherens junctions. Mechanical tension also triggers TRIP6 and LIMD1 to bind and inhibit the Hippo pathway kinase LATS1. How TRIP6 and LIMD1 are recruited to adherens junctions in response to tension is not clear, but previous studies suggested that they could be regulated by the known mechanosensory proteins -catenin and vinculin at adherens junctions. We found that the three LIM domains of TRIP6 and LIMD1 are necessary and sufficient for tension-dependent localization to adherens junctions. The LIM domains of TRIP6, LIMD1, and certain other LIM domain proteins have been shown to bind to actin networks under strain/tension. Consistent with this, we show that TRIP6 and LIMD1 colocalize with the ends of actin fibers at adherens junctions. Point mutations in a key conserved residue in each LIM domain that are predicted to impair binding to f-actin under strain inhibits TRIP6 and LIMD1 localization to adherens junctions and their ability to bind to and recruit LATS1 to adherens junctions. Together these results show that the ability of TRIP6 and LIMD1 to bind to strained actin underlies their ability to localize to adherens junctions and regulate LATS1 in response to mechanical tension.

cell biology↗

bioRxiv2022

Multicellular Aligned Bands Disrupt Global Collective Cell Behavior

Mechanical stress patterns emerging from collective cell behavior have been shown to play critical roles in morphogenesis, tissue repair, and cancer metastasis. In our previous work utilizing microcontact printing to geometrically constrain valvular interstitial cell monolayers into specific shapes, we demonstrated that the general patterns of observed cell alignment, size, and apoptosis correlate with predicted mechanical stress fields if nonuniform cell properties are used in the computational models. However, these radially symmetric models did not predict the substantial heterogeneity in cell behavior observed in individual circular aggregates. The goal of this study is to determine how the heterogeneities in cell behavior emerge over time and diverge from the predicted collective cell behavior. Cell-cell interactions in circular multicellular aggregates of valvular interstitial cells were studied with time-lapse imaging ranging from hours to days, and migration, proliferation, and traction stresses were measured. Our results indicate that individual elongated cells create strong local alignment within pre-confluent cell populations on the microcontact printed protein islands. These cells influence the alignment of additional cells to create dense, locally aligned bands of cells which disrupt the global behavior. Cells are highly elongated at the endpoints of the bands yet have decreased spread area in the middle and reduced mobility. Although traction stresses at the endpoints of bands are enhanced, even to the point of detaching aggregates from the culture surface, the cells in dense bands exhibit reduced proliferation, less nuclear YAP, and increased apoptotic rates indicating a low stress environment. These findings suggest that strong local cell-cell interactions between primary fibroblastic cells can disrupt the global collective cellular behavior leading to substantial heterogeneity of cell behaviors in constrained monolayers. This local emergent behavior within aggregated fibroblasts may play an important role in development and disease of connective tissues.

bioengineering↗

bioRxiv2017

TRIP6 inhibits the Hippo signaling pathway in response to tension at adherens junctions

The transcriptional co-activator YAP controls cell proliferation, survival, and tissue regeneration in response to changes in the mechanical environment. It is not known how mechanical stimuli such as tension are sensed and how the signal is transduced to control YAP activity. Here we show that the LIM domain protein TRIP6 acts as part of a mechanotransduction pathway at adherens junctions to promote YAP activity by inhibiting the LATS1/2 kinases. Previous studies showed that vinculin at adherens junctions becomes activated by mechanical tension. We show that vinculin inhibits Hippo signaling by recruiting TRIP6 to adherens junctions and stimulating its binding to and inhibition of LATS1/2 in response to tension. TRIP6 competes with MOB1 for binding to LATS1/2 thereby blocking MOB1 from recruiting the LATS1/2 activating kinases MST1/2. Together these findings reveal a novel mechanotransduction cascade that transduces tension signals sensed at adherens junctions to control Hippo pathway signaling.

cell biology↗