TRIP6 is required for tension at adherens junctions

Abstract

Hippo signaling mediates influences of cytoskeletal tension on organ growth. TRIP6 and LIMD1 have each been identified as being required for tension-dependent inhibition of the Hippo pathway LATS kinases and their recruitment to adherens junctions, but the relationship between TRIP6 and LIMD1 was unknown. Using siRNA-mediated gene knockdown we show that TRIP6 is required for LIMD1 localization to adherens junctions, whereas LIMD1 is not required for TRIP6 localization. TRIP6, but not LIMD1, is also required for recruitment of Vinculin and VASP to adherens junctions. Knockdown of TRIP6 or Vinculin, but not of LIMD1, also influences the localization of myosin and F-actin. In TRIP6 knockdown cells actin stress fibers are lost apically but increased basally, and there is a corresponding increase in recruitment of Vinculin and VASP to basal focal adhesions. Our observations identify a role for TRIP6 in organizing F-actin and maintaining tension at adherens junctions that could account for its influence on LIMD1 and LATS. They also suggest that focal adhesions and adherens junctions compete for key proteins needed to maintain attachments to contractile F-actin.

Förster resonance energy transfer efficiency of the vinculin tension sensor in cultured primary cortical neuronal growth cones

“…These sensors have been utilized successfully in epithelial cells where they have shed light on tension-driven regulation of focal adhesions 21 and adherens junctions. 14 , 22 In neuronal cells, the use of molecular tension probes has been relatively limited. A molecular probe was developed to measure actin tension and axonal growth in response to nerve growth factor and glial scar inhibitors in pheochromocytoma 12 (PC12) cells and to study the role of talin and E-cadherin in this response.…”

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

“…To test whether the ability to bind strained actin is also important for TRIP6 and LIMD1 recruitment of LATS1 to adherens junctions, we examined the phenotype of TRIP6 and LIMD1 knockout MCF10A cells rescued by their respective wild-type or tension sensing mutant. To our surprise, TRIP6 knockout cells (TRIP6-KO) did not show the clear defects in localization of LATS1 and LIMD1 to adherens junctions (not shown) that were previously reported using siRNA or sgRNA to knockdown TRIP6 (4,21). The reason for this difference is not clear and was observed in multiple independent knockout clones.…”

“…Previous studies showed that TRIP6 and LIMD1 play a central role in tension dependent regulation of Hippo signaling (4, 5, 21). Both proteins localize to adherens junctions in a tension dependent manner, where they are required to recruit and inhibit LATS1.…”

Analysis of the Drosophila Ajuba LIM protein defines functions for distinct LIM domains

“…One mechanism through which cytoskeletal tension modulates Hippo signaling involves the tension-dependent recruitment and inhibition of Wts at AJ, which is mediated by Jub. This was first discovered in Drosophila wing imaginal discs [ 18 ], but is conserved in mammalian cells, as LIMD1 can recruit and inhibit LATS kinases at AJ in MCF10A cells when there is tension in the actin cytoskeleton [ 19 , 37 , 38 ]. The recruitment of Wts to AJ by Jub sequesters it from upstream activators of Hippo signaling [ 39 ].…”