Rab46 integrates Ca2+ and histamine signaling to regulate selective cargo release from Weibel-Palade bodies

Abstract

Endothelial cells selectively release cargo stored in Weibel-Palade bodies (WPBs) to regulate vascular function, but the underlying mechanisms are poorly understood. Here we show that histamine evokes the release of the proinflammatory ligand, P-selectin, while diverting WPBs carrying non-inflammatory cargo away from the plasma membrane to the microtubule organizing center. This differential trafficking is dependent on Rab46 (CRACR2A), a newly identified Ca2+-sensing GTPase, which localizes to a subset of P-selectin–negative WPBs. After acute stimulation of the H1 receptor, GTP-bound Rab46 evokes dynein-dependent retrograde transport of a subset of WPBs along microtubules. Upon continued histamine stimulation, Rab46 senses localized elevations of intracellular calcium and evokes dispersal of microtubule organizing center–clustered WPBs. These data demonstrate for the first time that a Rab GTPase, Rab46, integrates G protein and Ca2+ signals to couple on-demand histamine signals to selective WPB trafficking.

Rabs in Signaling and Embryonic Development

“…This increased cytosolic Ca 2+ level activated nuclear factor of activated T cells 1 (NFATc1) and promoted osteoblast differentiation [19]. Rab46, another Rab with a CRAC domain, plays a role in the integration of Ca 2+ signals [20]. During histamine stimulation of endothelial cells, Rab46 induced retrograde trafficking of a subpopulation of Weibel-Palade bodies (WPBs) along the microtubules to the microtubule organizing center (MTOC).…”

“…This retrograde transport of WPBs is Ca 2+ -independent. However, the dispersion of WPBs accumulated at the MTOC required Ca 2+ capture by Rab46, leading to Rab46 detachment from the microtubules [20].…”

Neutrophil recruitment and intracellular vesicle transport: A short overview

“…This was the first report that directly related the function of a Rab protein to the regulation of selectin surface expression. Thereafter, Rab46 was shown to be involved in the differential regulation of histamine‐evoked WPB release by co‐localizing with P‐selectin‐negative WPBs driving away the non‐inflammatory cargo from the plasma membrane through retrograde transportation along microtubules 36 …”

Identification of novel Rab46 effector proteins

“…To date only three Ca 2+ -sensing GTPases (Rab44; Rab45 (RASEF) and Rab46 (CRACR2A)) have been reported. These Rabs play roles in trafficking events in osteoclasts (Rab44) (Yamaguchi et al, 2018), cancer cells (Rab45) (Nakamura et al, 2011), endothelial cells (ECs) and immune cells (Rab46) (Miteva et al, 2019;Srikanth et al, 2016). Their ability to sense changes in intracellular Ca 2+ implies that not only do these proteins have the ability to regulate intracellular trafficking events, but they could provide spatial and temporal regulation in resp onse to signalling events (allowing a Ca 2+ sensor to be in the right place at the right time) thereby providing a rapid link between intracellular signalling and vesicular transport.…”

“…We discovered Rab46 (CRACR2A-L) in ECs (Wilson et al, 2015) and described its important function in coupling stimuli to the appropriate release of cargo from endothelial-specific storage organelles (Weibel-Palade bodies: WPBs) (Miteva et al, 2019). In response to histamine, but not thrombin, Rab46 diverts a subpopulation of WPBs, carrying cargo superfluous to a histamine (immune) response, away from the plasma membrane to the microtubule organising centre (MTOC), inhibiting cargo release and thus preventing an all -out thrombotic response.…”