Nav1.5 regulates breast tumor growth and metastatic dissemination in vivo

James

Suman³

et al. 2019

Preprint

Self Cite

Ion channels can regulate the plasma membrane potential (Vm) and cell migration as a result of altered ion flux. However, the mechanism by which Vm regulates motility remains unclear.Here, we show that the Nav1.5 sodium channel carries persistent inward Na + current which depolarizes the resting Vm at the timescale of minutes. This Nav1.5-dependent Vm depolarization increases Rac1 colocalization with phosphatidylserine, to which it is anchored at the leading edge of migrating cells, promoting Rac1 activation. A genetically-encoded FRET biosensor of Rac1 activation shows that depolarization-induced Rac1 activation results in acquisition of a motile phenotype. By identifying Nav1.5-mediated Vm depolarization as a regulator of Rac1 activation, we link ionic and electrical signaling at the plasma membrane to small GTPase-dependent cytoskeletal reorganization and cellular migration. We uncover a novel and unexpected mechanism for Rac1 activation, which fine tunes cell migration in response to ionic and/or electric field changes in the local microenvironment.

Section: Rna Interferencementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Voltage-dependent activation of Rac1 by Na_v1.5 channels promotes cell migration

James

Suman³

et al. 2019

Preprint

Self Cite

“…Although the present findings are not adequate to answer these questions, in those tissues where we have directly recorded BK currents or tested for coassembly between LRRC26 and BK α-subunits, LRRC26 appears to be a critical regulatory component of BK channels. Given that a large number of ion channels have been implicated in tumor growth regulation, including KCa3.1 (47,48), calcium channels (49), sodium channels (50), and a variety of K + channels (51,52), these associations raise the possibility that specific ion channels per se may not be intrinsically related to tumor growth regulation, but that some aspect of membrane potential regulation, perhaps linked to cell cycle regulation, is the determinant of whether a given ion channel may promote or impede tumor growth.…”

Section: Potential Roles Of Lrrc26-containing Bk Channels In Tumor Grmentioning

confidence: 99%

Knockout of the LRRC26 subunit reveals a primary role of LRRC26-containing BK channels in secretory epithelial cells

Proc. Natl. Acad. Sci. U.S.A.

González-Pérez

Mukaibo

et al. 2017

Leucine-rich-repeat-containing protein 26 (LRRC26) is the regulatory γ1 subunit of Ca 2+ -and voltage-dependent BK-type K + channels. BK channels that contain LRRC26 subunits are active near normal resting potentials even without Ca 2+ , suggesting they play unique physiological roles, likely limited to very specific cell types and cellular functions. By using Lrrc26 KO mice with a β-gal reporter, Lrrc26 promoter activity is found in secretory epithelial cells, especially acinar epithelial cells in lacrimal and salivary glands, and also goblet and Paneth cells in intestine and colon, although absent from neurons. We establish the presence of LRRC26 protein in eight secretory tissues or tissues with significant secretory epithelium and show that LRRC26 protein coassembles with the pore-forming BK α-subunit in at least three tissues: lacrimal gland, parotid gland, and colon. In lacrimal, parotid, and submandibular gland acinar cells, LRRC26 KO shifts BK gating to be like α-subunit-only BK channels. Finally, LRRC26 KO mimics the effect of SLO1/BK KO in reducing [K + ] in saliva. LRRC26-containing BK channels are competent to contribute to resting K + efflux at normal cell membrane potentials with resting cytosolic Ca 2+ concentrations and likely play a critical physiological role in supporting normal secretory function in all secretory epithelial cells.L arge-conductance, voltage-and Ca 2+ -regulated BK-type channels are widely expressed proteins, found not only in excitable cells, such as neurons, muscle, and endocrine cells, but also nonexcitable cells, including salivary (1) and lacrimal gland (2) acinar cells, and colonic crypt cells (3). Given the almost ubiquitous expression of BK channels among cells that play quite distinct physiological roles, it is particularly important to define the specific properties of BK channels in a given cell type and determine what the specific physiological role played by BK channels in a given cell may be. A hallmark of BK channels is their dual regulation by both membrane voltage and cytosolic Ca 2+ (4), both properties embedded within the tetramer of pore-forming α-subunits of each BK channel (5). However, the specific range of voltages over which a BK channel is active at a given Ca 2+ concentration is markedly dependent on the identity of regulatory subunits that can coassemble with the α-subunit in the mature channel complex. Of the two families of known BK regulatory subunits, β (6-11) and γ (12-14), an important feature of many of these subunits is the ability to shift the range of activation voltages at a given Ca 2+ . Although there is growing information about the loci of expression and functional roles of BK channels containing specific β-subunits (15), much less is known about those BK channels containing the γ1 (LRRC26, leucine-rich-repeat-containing subunit 26) subunit. However, LRRC26 is particularly fascinating because it causes the largest shift in BK gating (approximately −120 mV) of any known non-pore-forming regulatory subunit, resulting in BK channels that...

“…Brains (or slices, following termination of electrophysiological experiments) were placed in fixative at 4 ˚C for >48 h and were then washed and sectioned at 20-60 µm. Control mammary tumour and naïve spleen sections were from tissue collected as part of other studies (37). The following primary antibodies were used as described previously (40)…”

Section: Immunohistochemistry and Confocal Microscopymentioning

confidence: 99%

Metastatic breast cancer cells induce altered microglial morphology and electrical excitabilityin vivo

Simon

Marrison

et al. 2019

Preprint

Self Cite

Background: An emerging problem in the treatment of breast cancer is the increasing incidence of metastases to the brain. Metastatic brain tumours are incurable and can cause epileptic seizures and cognitive impairment, so better understanding of this niche, and the cellular mechanisms, is urgently required. Microglia are the resident brain macrophage population, becoming "activated" by neuronal injury, eliciting an inflammatory response.Microglia promote proliferation, angiogenesis and invasion in brain tumours and metastases.However, the mechanisms underlying microglial involvement appear complex and better models are required to improve understanding of function.Methods: Here, we sought to address this need by developing a model to study metastatic breast cancer cell-microglial interactions using intravital imaging combined with ex vivo electrophysiology. We implanted an optical window on the parietal bone to facilitate observation of cellular behaviour in situ in the outer cortex of heterozygous Cx3cr1 GFP/+ mice.Results: We detected GFP-expressing microglia in Cx3cr1 GFP/+ mice up to 350 µm below the window without significant loss of resolution. When DsRed-expressing metastatic MDA-MB-231 breast cancer cells were implanted in Matrigel under the optical window, significant accumulation of activated microglia around invading tumour cells could be observed. This inflammatory response resulted in significant cortical disorganisation and aberrant spontaneously-occurring local field potential spike events around the metastatic site.Conclusions: These data suggest that peritumoral microglial activation and accumulation may play a critical role in local tissue changes underpinning aberrant cortical activity, which offers a possible mechanism for the disrupted cognitive performance and seizures seen in patients with metastatic breast cancer.