Limits...
Differential effects of antidepressants escitalopram versus lithium on Gs alpha membrane relocalization.

Donati RJ, Schappi J, Czysz AH, Jackson A, Rasenick MM - BMC Neurosci (2015)

Bottom Line: Results indicate that escitalopram was effective at liberating Gsα from lipid rafts while lithium was not.The results of this study indicate that the mood stabilizing agent, lithium, and the selective serotonin reuptake inhibitor, escitalopram, act on their cellular targets through mutually exclusive pathways.These results also validate the hypothesis that translocation of Gsα from lipid rafts could serve as a biosignature for antidepressant action.

View Article: PubMed Central - PubMed

Affiliation: Departments of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL, 60612-7342, USA. rdonati@ico.edu.

ABSTRACT

Background: Plasma membrane localization can play a significant role in the ultimate function of certain proteins. Specific membrane domains like lipid rafts have been shown to be inhibitory domains to a number of signaling proteins, including Gsα, and chronic antidepressant treatment facilitates Gs signaling by removing Gsα form lipid rafts. The intent of this study is to compare the effects of the selective serotnin reuptake inhibitor, escitalopram, with that of the mood stabilizing drug, lithium.

Results: There are a number of mechanisms of action proposed for lithium as a mood stabilizing agent, but the interactions between G proteins (particularly Gs) and mood stabilizing drugs are not well explored. Of particular interest was the possibility that there was some effect of mood stabilizers on the association between Gsα and cholesterol-rich membrane microdomains (lipid rafts), similar to that seen with long-term antidepressant treatment. This was examined by biochemical and imaging (fluorescence recovery after photobleaching: FRAP) approaches. Results indicate that escitalopram was effective at liberating Gsα from lipid rafts while lithium was not.

Conclusions: There are a number of drug treatments for mood disorders and yet there is no unifying hypothesis for a cellular or molecular basis of action. It is evident that there may in fact not be a single mechanism, but rather a number of different mechanisms that converge at a common point. The results of this study indicate that the mood stabilizing agent, lithium, and the selective serotonin reuptake inhibitor, escitalopram, act on their cellular targets through mutually exclusive pathways. These results also validate the hypothesis that translocation of Gsα from lipid rafts could serve as a biosignature for antidepressant action.

No MeSH data available.


Related in: MedlinePlus

FRAP suggests increased release of GFP-Gsα from lipid rafts after chronic antidepressant but not lithium treatment. a Typical course of photobleaching with representative images of cell before photobleaching (t = −3 s), immediately after photobleaching (t = 0 s), and after maximal recovery of fluorescence (t = 45 s). b Demonstration of typical fluorescence recovery after photobleaching in cells treated with escitalopram 10 µM or LiCl 3 mM for 72 h as described in “Methods”. Yellow arrows indicate area of bleach and recovery.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
getmorefigures.php?uid=PMC4499192&req=5

Fig3: FRAP suggests increased release of GFP-Gsα from lipid rafts after chronic antidepressant but not lithium treatment. a Typical course of photobleaching with representative images of cell before photobleaching (t = −3 s), immediately after photobleaching (t = 0 s), and after maximal recovery of fluorescence (t = 45 s). b Demonstration of typical fluorescence recovery after photobleaching in cells treated with escitalopram 10 µM or LiCl 3 mM for 72 h as described in “Methods”. Yellow arrows indicate area of bleach and recovery.

Mentions: Lateral mobility within the plasma membrane of Gsα as determined by fluorescence recovery after photobleaching (FRAP), changed following 1–3 days (depending on concentration) of antidepressant treatment [12]. Specifically, the half-time to recovery of GFP-Gsα is increased, likely due the increased association of Gsα, with the slow-moving adenylyl cyclase. In contrast, FRAP of GFP-Giα1 was unchanged after antidepressant treatment. A typical membrane bleaching and recovery of fluorescence is shown in Figure 3a. Escitalopram treated cells demonstrate a shorter total recovery (increased “immobile fraction”), perhaps because Gsα is bound to adenylyl cyclase (Figure 3b). Additionally, escitalopram treated cells have a less steep recovery curve than either control or lithium treated cells, which have similarly shaped curves. That is, they recover their fluorescence more slowly (increased half time of recovery). Figure 4 shows GFP-Gsα FRAP after 3 days of treatment with lithium chloride (3 mM), valproic acid (300 μM), escitalopram (10 μM), or escitalopram plus lithium combined (same doses as individual treatments with these compounds). While lithium and valproic acid treatment show no effect on Gsα membrane mobility compared to vehicle, treatment with escitalopram or escitalopram plus lithium shows the characteristic slowing of Gsα mobility as demonstrated by an increase in recovery half-time compared to vehicle (p < 0.0005 for escitalopram and p < 0.0005 for escitalopram plus lithium). In contrast, FRAP of GFP-Giα1 is unaltered by the aforementioned treatments (Figure 5), suggesting again that the effects of these drugs are not mediated through actions on Giα1.Figure 3


Differential effects of antidepressants escitalopram versus lithium on Gs alpha membrane relocalization.

Donati RJ, Schappi J, Czysz AH, Jackson A, Rasenick MM - BMC Neurosci (2015)

FRAP suggests increased release of GFP-Gsα from lipid rafts after chronic antidepressant but not lithium treatment. a Typical course of photobleaching with representative images of cell before photobleaching (t = −3 s), immediately after photobleaching (t = 0 s), and after maximal recovery of fluorescence (t = 45 s). b Demonstration of typical fluorescence recovery after photobleaching in cells treated with escitalopram 10 µM or LiCl 3 mM for 72 h as described in “Methods”. Yellow arrows indicate area of bleach and recovery.
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4499192&req=5

Fig3: FRAP suggests increased release of GFP-Gsα from lipid rafts after chronic antidepressant but not lithium treatment. a Typical course of photobleaching with representative images of cell before photobleaching (t = −3 s), immediately after photobleaching (t = 0 s), and after maximal recovery of fluorescence (t = 45 s). b Demonstration of typical fluorescence recovery after photobleaching in cells treated with escitalopram 10 µM or LiCl 3 mM for 72 h as described in “Methods”. Yellow arrows indicate area of bleach and recovery.
Mentions: Lateral mobility within the plasma membrane of Gsα as determined by fluorescence recovery after photobleaching (FRAP), changed following 1–3 days (depending on concentration) of antidepressant treatment [12]. Specifically, the half-time to recovery of GFP-Gsα is increased, likely due the increased association of Gsα, with the slow-moving adenylyl cyclase. In contrast, FRAP of GFP-Giα1 was unchanged after antidepressant treatment. A typical membrane bleaching and recovery of fluorescence is shown in Figure 3a. Escitalopram treated cells demonstrate a shorter total recovery (increased “immobile fraction”), perhaps because Gsα is bound to adenylyl cyclase (Figure 3b). Additionally, escitalopram treated cells have a less steep recovery curve than either control or lithium treated cells, which have similarly shaped curves. That is, they recover their fluorescence more slowly (increased half time of recovery). Figure 4 shows GFP-Gsα FRAP after 3 days of treatment with lithium chloride (3 mM), valproic acid (300 μM), escitalopram (10 μM), or escitalopram plus lithium combined (same doses as individual treatments with these compounds). While lithium and valproic acid treatment show no effect on Gsα membrane mobility compared to vehicle, treatment with escitalopram or escitalopram plus lithium shows the characteristic slowing of Gsα mobility as demonstrated by an increase in recovery half-time compared to vehicle (p < 0.0005 for escitalopram and p < 0.0005 for escitalopram plus lithium). In contrast, FRAP of GFP-Giα1 is unaltered by the aforementioned treatments (Figure 5), suggesting again that the effects of these drugs are not mediated through actions on Giα1.Figure 3

Bottom Line: Results indicate that escitalopram was effective at liberating Gsα from lipid rafts while lithium was not.The results of this study indicate that the mood stabilizing agent, lithium, and the selective serotonin reuptake inhibitor, escitalopram, act on their cellular targets through mutually exclusive pathways.These results also validate the hypothesis that translocation of Gsα from lipid rafts could serve as a biosignature for antidepressant action.

View Article: PubMed Central - PubMed

Affiliation: Departments of Physiology and Biophysics, College of Medicine, University of Illinois at Chicago, Chicago, IL, 60612-7342, USA. rdonati@ico.edu.

ABSTRACT

Background: Plasma membrane localization can play a significant role in the ultimate function of certain proteins. Specific membrane domains like lipid rafts have been shown to be inhibitory domains to a number of signaling proteins, including Gsα, and chronic antidepressant treatment facilitates Gs signaling by removing Gsα form lipid rafts. The intent of this study is to compare the effects of the selective serotnin reuptake inhibitor, escitalopram, with that of the mood stabilizing drug, lithium.

Results: There are a number of mechanisms of action proposed for lithium as a mood stabilizing agent, but the interactions between G proteins (particularly Gs) and mood stabilizing drugs are not well explored. Of particular interest was the possibility that there was some effect of mood stabilizers on the association between Gsα and cholesterol-rich membrane microdomains (lipid rafts), similar to that seen with long-term antidepressant treatment. This was examined by biochemical and imaging (fluorescence recovery after photobleaching: FRAP) approaches. Results indicate that escitalopram was effective at liberating Gsα from lipid rafts while lithium was not.

Conclusions: There are a number of drug treatments for mood disorders and yet there is no unifying hypothesis for a cellular or molecular basis of action. It is evident that there may in fact not be a single mechanism, but rather a number of different mechanisms that converge at a common point. The results of this study indicate that the mood stabilizing agent, lithium, and the selective serotonin reuptake inhibitor, escitalopram, act on their cellular targets through mutually exclusive pathways. These results also validate the hypothesis that translocation of Gsα from lipid rafts could serve as a biosignature for antidepressant action.

No MeSH data available.


Related in: MedlinePlus