Summary The cytosolic protein α–catenin is a postulated force-transducer at cadherin complexes [1]. The demonstration of force activation, identification of consequent downstream events in live cells, and development of tools to study these dynamic processes in living cells are central to elucidating the role of α–catenin in cellular mechanics and tissue function [2–10]. Here we demonstrate that α–catenin is a force-activatable mechano-transducer at cell-cell junctions, using an engineered α-catenin conformation sensor, based on fluorescence resonance energy transfer (FRET). This sensor reconstitutes α-catenin-dependent functions in α-catenin depleted cells, and recapitulates the behavior of the endogenous protein. Dynamic imaging of cells expressing the sensor demonstrated that α-catenin undergoes immediate, reversible conformational switching, in direct response to different mechanical perturbations of cadherin adhesions. Combined magnetic twisting cytometry with dynamic FRET imaging [11] revealed rapid, local conformational switching, upon the mechanical stimulation of specific cadherin bonds. At acutely stretched cell-cell junctions, the immediate, reversible conformational change further reveals that α-catenin behaves like an elastic spring in series with cadherin and actin. The force-dependent recruitment of vinculin—a principal α-catenin effector—to junctions requires the vinculin-binding-site of the α–catenin sensor [1, 12–16]. In cells, the relative rates of force-dependent α–catenin conformation switching and vinculin recruitment reveal that α–catenin activation and vinculin recruitment occur sequentially rather than in a concerted process, with vinculin accumulation being significantly slower. This engineered α-catenin sensor revealed that α–catenin is a reversible, stretch-activatable sensor that mechanically links cadherin complexes and actin, and is an indispensable player in cadherin-specific mechano-transduction at intercellular junctions.

Ischemia induces angiogenesis as a compensatory response. Although ischemia is known to causes synthesis and release of calcitonin gene-related peptide (CGRP), it is not clear whether CGRP regulates angiogenesis under ischemia and how does it function. Thus we investigated the role of CGRP in angiogenesis and the involved mechanisms. We found that CGRP level was increased in the rat hindlimb ischemic tissue. The expression of exogenous CGRP by adenovirus vectors enhanced blood flow recovery and increased capillary density in ischemic hindlimbs. In vitro, CGRP promoted human umbilical vein endothelial cell (HUVEC) tube formation and migration. Further more, CGRP activated AMP-activated protein kinase (AMPK) both in vivo and in vitro, and pharmacological inhibition of CGRP and cAMP attenuated the CGRP-activated AMPK in vitro. CGRP also induced endothelial nitric oxide synthase (eNOS) phosphorylation in HUVECs at Ser1177 and Ser633 in a time-dependent manner, and such effects were abolished by AMPK inhibitor Compound C. As well, Compound C blocked CGRP-enhanced HUVEC tube formation and migration. These findings indicate that CGRP promotes angiogenesis by activating the AMPK-eNOS pathway in endothelial cells.

The HSS-induced [Ca(2+)](i) increase consists of two well-co-ordinated phases with different sources and mechanisms: (i) an early phase due to the calcium influx across the PM which is dependent on the mechanical impact and cytoskeletal support and (ii) a late phase originated from the ER-calcium efflux which is regulated by the Src, PLC, and IP(3)R signalling pathway. Therefore, our work presented new molecular-level insights into systematic understanding of mechanotransduction in cardiovascular systems.

BackgroundGanglionated plexi (GP) ablation has been become an adjunct to pulmonary vein isolation (PVI). This study describes the long-term results of minimally invasive surgical PVI, ablation of GPs, and exclusion of the left atrial appendage for atrial fibrillation (AF).MethodsLong-term follow-up of 55 months was performed in 139 consecutive patients (age 58.3±20.8 years) with symptomatic, drug-refractory lone AF who underwent minimally invasive surgical PVI, GPs ablation, and exclusion of the left atrial appendage. Success was defined as freedom from AF, atrial flutter, or atrial tachycardia off antiarrhythmic drugs.ResultsAF was paroxysmal in 77.7%, persistent in 12.2% and long-standing persistent in 10.1%. Single-procedure success rate was 71.7%, 59.4% and 46.6% at 12, 24 and 60 months respectively. Single-procedure success rate was 72.9%, 62.6% and 51.8% for paroxysmal AF, 64.7%, 35.3%, and 28.2% for persistent AF, 71.4%, 64.3% and 28.6% for long-standing persistent AF at 12, 24 and 60 months respectively. Duration of AF>24 months (hazard ratio [HR]: 3.09, 95% confidence interval [CI]: 1.51 to 6.32; p = 0.002), left atrial diameter≥40 mm (HR: 4.03, 95% CI: 1.88 to 8.65; p<0.001), early recurrence of AF (HR: 4.66, 95% CI: 2.25 to 9.63; p<0.001) independently predicted long-term recurrence of AF. There was no procedure-related death. One patient converted to median sternotomy because of uncontrolled bleeding. Two patients underwent perioperative cerebrovascular events.ConclusionsAt nearly 5-year of clinical follow-up, single-procedure success rate of minimally invasive surgical PVI with GP ablation was 51.8% for paroxysmal AF, 28.2% for persistent AF, 28.6% for long-standing persistent AF after initial procedure. Patients with AF duration≤24 months, left atrial diameter<40 mm and no early recurrence of AF, had favorable outcomes.