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D J Benos

Publications and source records attributed to D J Benos.

At least 91 records · Page 5Linked to original sources
PubMed1996

A biologic function for an "orphan" messenger: D-myo-inositol 3,4,5,6-tetrakisphosphate selectively blocks epithelial calcium-activated chloride channels.

Inositol phosphates are a family of water-soluble intracellular signaling molecules derived from membrane inositol phospholipids. They undergo a variety of complex interconversion pathways, and their levels are dynamically regulated within the cytosol in response to a variety of agonists. Relatively little is known about the biological function of most members of this family, with the exception of inositol 1,4,5-trisphosphate. Specifically, the biological functions of inositol tetrakisphosphates are largely obscure. In this paper, we report that D-myo-inositol 3,4,5,6-tetrakisphosphate (D-Ins(3,4,5,6)P4) has a direct biphasic (activation/inhibition) effect on an epithelial Ca(2+)-activated chloride channel. The effect of D-Ins(3,4,5,6)P4 is not mimicked by other inositol tetrakisphosphate isomers, is dependent on the prevailing calcium concentration, and is influenced when channels are phosphorylated by calmodulin kinase II. The predominant effect of D-Ins(3,4,5,6)P4 on phosphorylated channels is inhibitory at levels of intracellular calcium observed in stimulated cells. Our findings indicate the biological function of a molecule hitherto considered as an "orphan" messenger. They suggest that the molecular target for D-Ins(3,4,5,6)P4 is a plasma membrane Ca(2+)-activated chloride channel. Regulation of this channel by D-Ins(3,4,5,6)P4 and Ca2+ may have therapeutic implications for the disease states of both diabetic nephropathy and cystic fibrosis.

Adenosine Triphosphate↗
PubMed1996

Regulation of epithelial sodium channels by short actin filaments.

Cytoskeletal elements play an important role in the regulation of ion transport in epithelia. We have studied the effects of actin filaments of different length on the alpha, beta, gamma-rENaC (rat epithelial Na+ channel) in planar lipid bilayers. We found the following. 1) Short actin filaments caused a 2-fold decrease in unitary conductance and a 2-fold increase in open probability (Po) of alpha,beta,gamma-rENaC. 2) alpha,beta,gamma-rENaC could be transiently activated by protein kinase A (PKA) plus ATP in the presence, but not in the absence, of actin. 3) ATP in the presence of actin was also able to induce a transitory activation of alpha, beta,gamma-rENaC, although with a shortened time course and with a lower magnitude of change in Po. 4) DNase I, an agent known to prohibit elongation of actin filaments, prevented activation of alpha,beta,gamma-rENaC by ATP or PKA plus ATP. 5) Cytochalasin D, added after rundown of alpha,beta,gamma-rENaC activity following ATP or PKA plus ATP treatment, produced a second transient activation of alpha,beta,gamma-rENaC. 6) Gelsolin, a protein that stabilizes polymerization of actin filaments at certain lengths, evoked a sustained activation of alpha,beta,gamma-rENaC at actin/gelsolin ratios of <32:1, with a maximal effect at an actin/gelsolin ratio of 2:1. These results suggest that short actin filaments activate alpha, beta,gamma-rENaC. PKA-mediated phosphorylation augments activation of this channel by decreasing the rate of elongation of actin filaments. These results are consistent with the hypothesis that cloned alpha,beta,gamma-rENaCs form a core conduction unit of epithelial Na+ channels and that interaction of these channels with other associated proteins, such as short actin filaments, confers regulation to channel activity.

Actins↗
PubMed1996

Regulation of epithelial sodium channels by the cystic fibrosis transmembrane conductance regulator.

Cystic fibrosis airway epithelia exhibit enhanced Na+ reabsorption in parallel with diminished Cl- secretion. We tested the hypothesis that the cystic fibrosis transmembrane conductance regulator (CFTR) directly affects epithelial Na+ channel activity by co-incorporating into planar lipid bilayers immunopurified bovine tracheal CFTR and either heterologously expressed rat epithelial Na+ channel ( alpha,b eta,gamma-rENaC) or an immunopurified bovine renal Na+ channel protein complex. The single channel open probability (Po) of rENaC was decreased by 24% in the presence of CFTR. Protein kinase A (PKA) plus ATP activated CFTR, but did not have any effect on rENaC. CFTR also decreased the extent of elevation of the renal Na+ channel Po following PKA-mediated phosphorylation. Moreover, the presence of CFTR prohibited the inward rectification of the gating of this renal Na+ channel normally induced by PKA-mediated phosphorylation, thus down-regulating inward Na+ current. This interaction between CFTR and Na+ channels occurs independently of whether or not wild-type CFTR is conducting anions. However, the nonconductive CFTR mutant, G551D CFTR, cannot substitute for the wild-type molecule. Our results indicate that CFTR can directly down-regulate single Na+ channel activity, thus accounting, at least in part, for the observed differences in Na+ transport between normal and cystic fibrosis-affected airway epithelia.

Adenosine Triphosphate↗
PubMed1996

G-protein regulation of outwardly rectified epithelial chloride channels incorporated into planar bilayer membranes.

Experiments were designed to test if immunopurified outwardly rectified chloride channels (ORCCs) and the cystic fibrosis transmembrane conductance regulator (CFTR) incorporated into planar lipid bilayers are regulated by G-proteins. pertussis toxin (PTX) (100 ng/ml) + NAD (1 mM) + ATP (1 mM) treatment of ORCC and CFTR in bilayers resulted in a 2-fold increase in single channel open probability (Po) of ORCC but not of CFTR. Neither PTX, NAD, nor ATP alone affected the biophysical properties of either channel. Further, PTX conferred a linearity to the ORCC current-voltage curve, with a slope conductance of 80 +/- 3 picosiemens (pS) in the +/- 100 mV range of holding potentials. PKA-mediated phosphorylation of these PTX + NAD-treated channels further increased the Po of the linear 80-pS channels from 0.66 +/- 0.05 to >0.9, and revealed the presence of a small (16 +/- 2 pS) linear channel in the membrane. PTX treatment of a CFTR-immunodepleted protein preparation incorporated into bilayer membranes resulted in a similar increase in the Po of the larger conductance channel and restored PKA-sensitivity that was lost after CFTR immunodepletion. The addition of guanosine 5'-3-O-(thio)triphosphate (100 mum) to the cytoplasmic bathing solutions decreased the activity of the ORCC and increased its rectification at both negative and positive voltages. ADP-ribosylation of immunopurified material revealed the presence of a 41-kDa protein. These results demonstrate copurification of a channel-associated G-protein that is involved in the regulation of ORCC function.

Adenosine Diphosphate Ribose↗
PubMed1996

Regulation of a sodium channel-associated G-protein by aldosterone.

The action of aldosterone to increase apical membrane permeability in responsive epithelia is thought to be due to activation of sodium channels. This channel is regulated, in part, by G-proteins, but it is not known if this mechanism is regulated by aldosterone. We report that aldosterone stimulates the expression of the 41-kDa alphai3 subunit of the heterotrimeric GTP-binding proteins in A-6 cells. Both mRNA and the total amount of this protein are increased by aldosterone. The G-protein is palmitoylated in response to the steroid, and the newly synthesized subunit is found to co-localize with the sodium channel. Aldosterone stimulation of sodium transport is significantly inhibited by inhibition of palmitoylation. These results suggest that aldosterone regulates sodium channel activity in epithelia through stimulation of the expression and post-translational targeting of a channel regulatory G-protein subunit.

Aldosterone↗
PubMed1996

HIV glycoprotein 120 enhances intercellular adhesion molecule-1 gene expression in glial cells. Involvement of Janus kinase/signal transducer and activator of transcription and protein kinase C signaling pathways.

It is well established that the two major glial cells in the central nervous system (CNS), astrocytes and microglia, are key participants in mediating the neurologic dysfunction associated with HIV infection of the CNS. In this study, we investigated the ability of the major envelope glycoprotein of HIV, glycoprotein 120 (gp120), to regulate intercellular adhesion molecule-1 (ICAM-1) expression in glial cells, because ICAM-1 is important in mediating immune responsiveness in the CNS, facilitating entry of HIV-infected cells into the CNS, and promoting syncytia formation. Our results indicate that gp120 enhances ICAM-1 gene expression in primary rat astrocytes, primary human astrocytes, a human astroglioma cell line CRT, and primary rat microglia. The signal transduction events involved in gp120-mediated enhancement of ICAM-1 appear to involve activation of both protein kinase C and tyrosine kinase, because inhibitors of protein kinase C and tyrosine kinase abrogate gp120-mediated ICAM-1 expression in both astrocytes and microglia. Moreover, gp120 induces tyrosine phosphorylation of signal transducer and activator of transcription (STAT-1 alpha) as well as the Janus kinase (JAK2) in glial cells. We also demonstrate that gp120-mediated ICAM-1 expression has functional significance, as it enhances the ability of monocytic cells to bind to gp120-stimulated human astrocytes in an ICAM-1/beta 2 integrin-dependent fashion. These results provide new insights into how gp120 can influence the involvement of glial cells in the pathogenesis of AIDS dementia complex.

Animals↗
PubMed1996

Triple-barrel organization of ENaC, a cloned epithelial Na+ channel.

A cloned rat epithelial Na+ channel (rENaC) was studied in planar lipid bilayers. Two forms of the channel were examined: channels produced by the alpha subunit alone and those formed by alpha, beta, and gamma subunits. The protein was derived from two sources: either from in vitro translation reaction followed by Sephadex column purification or from heterologous expression in Xenopus oocytes and isolation of plasma membranes. We found that either alpha-rENaC alone or alpha- in combination with beta- and gamma-rENaC, produced highly Na(+)-selective (PNa/PK = 10), amiloride-sensitive (Kamili = 170 nM), and mechanosensitive cation channels in planar bilayers. alpha-rENaC displayed a complicated gating mechanism: there was a nearly constitutively open 13-picosiemens (pS) state and a second 40-pS level that was achieved from the 13-pS level by a 26-pS transition. alpha-, beta-, gamma-rENaC showed primarily the 13-pS level. alpha-rENaC and alpha,beta,gamma-rENaC channels studied by patch clamp displayed the same gating pattern, albeit with > 2-fold lowered conductance levels, i.e. 6 and 18 pS, respectively. Upon treatment of either channel with the sulfhydryl reducing agent dithiothreitol, both channels fluctuated among three independent 13-pS sublevels. Bathing each channel with a high salt solution (1.5 M NaCl) produced stochastic openings of 19 and 38 pS in magnitude between all three conductance levels. Different combinations of alpha-, beta-, and gamma-rENaC in the reconstitution mixture did not produce channels of intermediate conductance levels. These findings suggest that functional ENaC is composed of three identical conducting elements and that their gating is concerted.

Animals↗
PubMed1996

Associated proteins and renal epithelial Na+ channel function.

The hypothesis that amiloride-sensitive Na+ channel complexes immunopurified from bovine renal papillary collecting tubules contain, as their core conduction component, an ENaC subunit, was tested by functional and immunological criteria. Disulfide bond reduction with dithiothreitol (DTT) of renal Na+ channels incorporated into planar lipid bilayers caused a reduction of single channel conductance from 40 pS to 13 pS, and uncoupled PKA regulation of this channel. The cation permeability sequence, as assessed from bi-ionic reversal potential measurements, and apparent amiloride equilibrium dissociation constant (K(amil)i) of the Na+ channels were unaltered by DTT treatment. Like ENaC, the DTT treated renal channel became mechanosensitive, and displayed a substantial decrease in K(amil)i following stretch (0.44 +/- 0.12 microM versus 6.9 +/- 1.0 microM). Moreover, stretch activation induced a loss in the channel's ability to discriminate between monovalent cations, and even allowed Ca2+ to permeate. Polyclonal antibodies generated against a fusion protein of alpha bENaC recognized a 70 kDa polypeptide component of the renal Na+ channel complex. These data suggest that ENaC is present in the immunopurified renal Na+ channel protein complex, and that PKA sensitivity is conferred by other associated proteins.

Amiloride↗
PubMed1996

The binding site on cochlear stereocilia for antisera raised against renal Na+ channels is blocked by amiloride and dihydrostreptomycin.

The mechanoelectrical transduction channels on hair cells have been suggested to be operated by tip links that are stretched when the hair bundle is deflected in the direction of the tallest row of stereocilia. Localising these channels is therefore an important test of this hypothesis. The transduction channels are known to be amiloride-sensitive and immunogold labelling with antibodies raised against the amiloride-sensitive epithelial Na+ channel from kidney (alpha NaCh), has suggested that sites with similar characteristics are located in the region where the tips of the shorter stereocilia appear to come into contact with the sides of the adjacent taller stereocilia rather than being associated directly with the tip links. Now, further immunocytochemical experiments have been performed to determine if amiloride and dihydrostreptomycin, both of which can block transduction, can affect this labelling. Immunofluorescent labelling of the stereocilia is obtained when surface preparations of the organ of Corti are fixed and incubated with alpha NaCh followed by an appropriate secondary antibody. This labelling is abolished by trypsinization prior to fixation but retained if the tissue is pretreated with amiloride and then trypsinized in its presence. Because amiloride is known to protect amiloride-binding sites from degradation by trypsin, these results suggest that alpha NaCh is revealing amiloride-binding sites on the stereocilia. Similarly, immunofluorescent labelling of the stereocilia is abolished if cochlear tissue is pretreated with dihydrostreptomycin (DHS) and fixed in its presence prior to incubation with alpha NaCh. Quantitative analysis of colloidal gold labelling using transmission electron microscopy shows that DHS treatment produces a significant reduction in the number of gold particles on stereocilia, especially in the region of contact between them. These results suggest that anti-Na+ recognises a site with characteristics similar to the mechanoelectrical transduction channels.

Amiloride↗
PubMed1996

Diversity and regulation of amiloride-sensitive Na+ channels.

Amiloride-sensitive Na+ channels play a vital role in many important physiological processes such as delineation of the final urine composition, sensory transduction, and whole-body Na+ homeostasis. These channels display a wide range of biophysical properties, and are regulated by cAMP-mediated second messenger systems. The first of these channels has recently been cloned. This cloned amiloride-sensitive Na+ channel is termined ENaC (Epithelial Na+ Channel) and, in heterologous cellular expression systems, displays a single channel conductance of 4 to 7 pS, a high PNa/PK (> 10), a high amiloride sensitivity (Ki(amil) = 150 nM), and relatively long open and closed times. ENaC may form the core conduction element of many of these functionally diverse forms of Na+ channel. The kinetic and regulatory differences between these channels may be due, in large measure, to unique polypeptides that associate with the core element, forming a functional channel unit.

Amiloride↗
PubMed1996

Protein kinase regulation of a cloned epithelial Na+ channel.

We examined the regulation of a cloned epithelial Na+ channel (alpha beta gamma-rENaC) by protein kinase A (PKA) and protein kinase C (PKC). Experiments were performed in Xenopus oocytes and in planar lipid bilayers. At a holding potential of -100 mV, amiloride-sensitive current averaged -1,279 +/- 111 nA (n = 7) in alpha beta gamma-rENaC-expressing oocytes. Currents in water-injected oocytes were essentially unresponsive to 10 microM amiloride. A 1-h stimulation of PKC with 100 nM of PMA inhibited whole-cell currents in Xenopus oocytes to 17.1 +/- 1.8, and 22.1 +/- 2.6% of control (n = 7), at holding potentials of -100 and +40 mV, respectively. Direct injection of purified PKC resulted in similar inhibition to that observed with PMA. Additionally, the inactive phorbol ester, phorbol-12-myristate-13-acetate, 4-O-methyl, was without effect on alpha beta gamma-rENaC currents. Pretreatment with the microtubule inhibitor colchicine (100 microM) did not modify the inhibitory effect of PMA; however, pretreatment with 20 microM cytochalasin B decreased the inhibitory action of PMA to < 20% of that previously observed. In vitro-synthesized alpha beta gamma-rENaC formed an amiloride-sensitive Na(+)-selective channel when incorporated into planar lipid bilayers. Addition of PKC, diacyl-glycerol, and Mg-ATP to the side opposite that which amiloride blocked, decreased the channel's open probability (Po) from 0.44 +/- 0.06 to 0.13 +/- 0.03 (n = 9). To study the effects of PKA on alpha beta gamma-rENaC expressed in Xenopus oocytes, cAMP levels were elevated with 10 microM forskolin and 1 mM isobutyl-methyl-xanthine. This cAMP-elevating cocktail did not cause any stimulation of alpha beta gamma-rENaC currents in either the inward or outward directions. This lack of activation was also observed in oocytes preinhibited with PMA and in oocytes pretreated with cytochalasin B and PMA. Neither alpha-rENaC nor alpha beta gamma-rENaC incorporated into planar lipid bilayers could be activated with PKA and Mg-ATP added to either side of the membrane, as Po remained at 0.63 +/- 0.06 (n = 7) and 0.45 +/- 0.05 (n = 9), respectively. We conclude that: alpha beta gamma-rENaC is inhibited by PKC, and that alpha beta gamma-rENaC is not activated by PKA.

Animals↗
PubMed1996

Introduction to medical physiology: cellular membranes and transmembrane transport of solutes and water.

This article summarizes the comments made in the introductory session of the Medical Physiology course taught at the University of Alabama School of Medicine. The main thesis is that learning physiology is easier when fundamental principles are first delineated. Four general principles of physiology (mass balance, force-flow, capacitance, and equilibrium) are discussed. Clinical medicine becomes more comprehensible when these basic principles are understood. Cellular Physiology is taught first because it forms the conceptual basis for what follows in the course. The idea that the root of clinical medicine lies in the basic sciences is emphasized.

Animals↗
PubMed1996

Liddle's disease: abnormal regulation of amiloride-sensitive Na+ channels by beta-subunit mutation.

Liddle's disease is an autosomal dominant genetic disorder characterized by severe low renin hypertension ("pseudoaldosteronism") that has been genetically linked to a locus on chromosome 16 encoding the beta-subunit of an amiloride-sensitive Na+ channel (ASSC) (15). Peripheral blood lymphocytes (PBL) express ASSC that are functionally indistinguishable from those expressed by Na(+)-reabsorbing renal epithelial cells (3, 5). The amiloride-sensitive Na+ conductance in PBL from affected and unaffected individuals from the original Liddle's pedigree was examined using whole cell patch clamp. Typically, the basal Na+ currents in cells from affected individuals were maximally activated. Basal Na+ currents in cells from unaffected individuals were minimal and could be maximally activated by superfusion with 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (CPT-cAMP). Affected cells could not be further stimulated with CPT-cAMP. Superfusion with a supermaximal concentration of amiloride (2 microM) inhibited both the cAMP-activated Na+ conductance in unaffected cells and the constitutively activated inward conductance in affected cells. Cytosolic addition of a peptide identical to the terminal 10 amino acids of the truncated beta-subunit normalized the cAMP-mediated but not the pertussis toxin-induced regulation of the mutant ASSC. The findings show that lymphocyte ASSC are constitutively activated in affected individuals, that a mutation of the beta-subunit alters ASSC responsiveness to specific regulatory effectors, and that the cellular mechanism responsible for the pathophysiology of Liddle's disease is abnormal regulation of Na+ channel activity. These findings have important diagnostic and therapeutic implications and provide a cellular phenotype for the diagnosis of pseudoaldosteronism.

Amiloride↗
PubMed1996

Peptide block of constitutively activated Na+ channels in Liddle's disease.

Hypertension is a multifactorial disorder that results in an increased risk of cardiovascular and end-stage renal disease. Liddle's disease represents a specific hypertensive disease and expresses itself in the human population as an autosomal dominant trait. Recent experimental evidence indicates that patients with Liddle's disease have constitutively active amiloride-sensitive Na+ channels and that these channels are phenotypically expressed in lymphocytes obtained from normal and affected members of the original Liddle's kindred. Linkage analysis indicates that this disease results from a deletion of the carboxy-terminal region of the beta-subunit of a recently cloned epithelial Na+ channel (ENaC). We report the successful immunopurification and reconstitution of both normal and constitutively active lymphocyte Na+ channels into planar lipid bilayers. These channels display all of the characteristics typical of renal Na+ channels, including sensitivity to protein kinase A phosphorylation. We demonstrate that gating of normal Na+ channels is removed by cytoplasmic trypsin digestion and that the constitutively active Liddle's Na+ channels are blocked by a beta- or gamma-ENaC carboxy-terminal peptide in a GTP-dependent fashion.

Amiloride↗
PubMed1996

Stretch modulates amiloride sensitivity and cation selectivity of sodium channels in human B lymphocytes.

Stretch-mediated regulation of amiloride-sensitive Na+ channels was examined in Epstein-Barr virus-transformed human B lymphocytes. Cation conductances were measured using whole cell patch-clamp techniques. Stretch activation, induced by increasing the hydrostatic pressure of the bath solution, immediately and reversibly increased both inward and outward ionic conductances once a threshold of 2-5 mmH2O was reached. Ionic substitutions confirmed that stretch enhanced membrane conductivity for both Na+ and K+. Amiloride (2 microM) completely prevented the response to elevated hydrostatic pressure; however, when amiloride was applied after stretch-induced activation, the sensitivity to amiloride was dramatically decreased (inhibitor concentration that reduces whole cell current by 50% of approximately 20 microM). Evidence that the currents induced by stretch were mediated by Na+ channels was provided by the lack of response to stretch in lymphocytes from patients with Liddle's syndrome, which is caused by expression of a truncated mutant of the beta-subunit of the amiloride-sensitive Na+ channel. Pretreatment with colchicine (0.5 mM, 30 min) prevented stretch-induced activation, which shows evidence of the involvement of the cytoskeleton. These data indicate that stretch regulates the conductance of amiloride-sensitive Na+ channels in immortalized human B lymphocytes and also alters its cationic selectivity and its sensitivity to amiloride.

Amiloride↗
PubMed1996

Biophysical and molecular properties of amiloride-inhibitable Na+ channels in alveolar epithelial cells.

The recent immunopurification and cloning of various lung Na+ channel proteins has provided the necessary tools to study Na+ transport at a fundamental level across a number of epithelial tissues. Various macroscopic measurements of Na+ transport have shown that Na+ ions enter the cytoplasm of alveolar cells mainly through amiloride-inhibitable Na+ channels. Molecular biology studies have shown the existence of three Na+ channel subunit mRNAs (alpha-, beta-, and gamma-rENaC) in mature fetal (FDLE) and adult alveolar type II (ATII) cells. Patch-clamp studies have demonstrated the existence of various types of amiloride-inhibitable Na+ channels, located in the apical membranes of FDLE and ATII cells. beta-Agonists and agents that enhance intracellular adenosine 3',5'-cyclic monophosphate levels increase the open probability of these channels, leading to increased Na+ transport across the alveolar epithelium in vivo. Immunopurification of a putative channel protein from adult ATII cells showed that it contains an amiloride-binding subunit with a molecular mass of 150 kDa. When this protein was reconstituted in planar lipid bilayers, it exhibited single channels with a conductance of 25 pS, which were moderately selective for Na+ over K+. The open probability of these channels was increased by the addition of protein kinase A (PKA) and ATP, and was decreased to the same extent by addition of [N-ethyl-N-isopropyl]-2'-4'-amiloride (EIPA) and amiloride (1 microM each) in the apical side of the bilayer, in agreement with the results of patch-clamp studies in ATII cells. Exposure of rats to sublethal hyperoxia increased alpha-rENaC mRNA and the functional expression of Na+ channels in alveolar epithelial cells and limited alveolar edema. These findings indicate that alveolar epithelial channels contain at least one family of amiloride-sensitive Na+ channel proteins, which displays a number of unique properties, including sensitivity to EIPA.

Amiloride↗
PubMed1996

Apical recruitment of CFTR in T-84 cells is dependent on cAMP and microtubules but not Ca2+ or microfilaments.

Previous studies from this laboratory have demonstrated that chloride transport induced by forskolin, but not ionomycin, in T84 cells is highly dependent on an intact microtubular network. Using an antibody raised against a region of the R domain of CFTR, we now show by indirect immunofluorescence that forskolin causes relocation of CFTR to the apical domain of T84 cells. T84 cells grown on transparent filters were incubated with agonists and/or cytoskeletal inhibitors prior to fixation, permeabilization, and staining with the antibody. A 30 second stimulation with forskolin (10 microM) caused a twofold increase in relative fluorescence intensity at the apical surface. In contrast, a 30 second exposure to ionomycin (2 microM), had no effect on the distribution of CFTR-related fluorescence. Incubation of the cells with nocodazole (33 microM), a microtubule disrupting agent, prevented the forskolin-induced rise in CFTR fluorescence at the apical surface. However, incubation of the cells with cytochalasin D, an actin inhibitor, was without effect on forskolin-related re-distribution of CFTR-associated fluorescence. In double label experiments using antibodies against both beta-tubulin and actin, CFTR-related fluorescence was found to co-localize with the microtubule network, but not with actin filaments. These observations are consistent with the microtubule-dependent acute recruitment of CFTR to the apical plasma membrane of T84 cells in response to elevations in intracellular cAMP.

Actin Cytoskeleton↗