Limits...
i-SNAREs: inhibitory SNAREs that fine-tune the specificity of membrane fusion.

Varlamov O, Volchuk A, Rahimian V, Doege CA, Paumet F, Eng WS, Arango N, Parlati F, Ravazzola M, Orci L, Söllner TH, Rothman JE - J. Cell Biol. (2003)

Bottom Line: A new functional class of SNAREs, designated inhibitory SNAREs (i-SNAREs), is described here.A striking pattern emerges in which certain subunits of the cis-Golgi SNAREpin function as i-SNAREs that inhibit fusion mediated by the trans-Golgi SNAREpin, and vice versa.Although the opposing distributions of the cis- and trans-Golgi SNAREs themselves could provide for a countercurrent fusion pattern in the Golgi stack, the gradients involved would be strongly sharpened by the complementary countercurrent distributions of the i-SNAREs.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular Biochemistry and Biophysics, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., Box 251, New York, NY 10021, USA.

ABSTRACT
A new functional class of SNAREs, designated inhibitory SNAREs (i-SNAREs), is described here. An i-SNARE inhibits fusion by substituting for or binding to a subunit of a fusogenic SNAREpin to form a nonfusogenic complex. Golgi-localized SNAREs were tested for i-SNARE activity by adding them as a fifth SNARE together with four other SNAREs that mediate Golgi fusion reactions. A striking pattern emerges in which certain subunits of the cis-Golgi SNAREpin function as i-SNAREs that inhibit fusion mediated by the trans-Golgi SNAREpin, and vice versa. Although the opposing distributions of the cis- and trans-Golgi SNAREs themselves could provide for a countercurrent fusion pattern in the Golgi stack, the gradients involved would be strongly sharpened by the complementary countercurrent distributions of the i-SNAREs.

Show MeSH

Related in: MedlinePlus

Design of tests for i-SNAREs. (A) The pairing of t-SNAREs composed of one syntaxin heavy chain and two nonsyntaxin light chains with cognate v-SNAREs on the opposite membranes mediates membrane fusion (control fusion). (B) To test whether the presence of additional SNAREs (candidate i-SNAREs) can modulate the activity of fusogenic SNARE complexes, we incorporated candidate i-SNAREs at increasing concentrations into t-SNARE–containing liposomes. (C) Fusion of each type of liposome is compared with control fusion, and is plotted as a function of the molar ratio of the candidate i-SNAREs to the t-SNARE. K50 is the molar ratio of the i-SNARE to the t-SNARE needed to reduce fusion by 50%.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2171956&req=5

fig1: Design of tests for i-SNAREs. (A) The pairing of t-SNAREs composed of one syntaxin heavy chain and two nonsyntaxin light chains with cognate v-SNAREs on the opposite membranes mediates membrane fusion (control fusion). (B) To test whether the presence of additional SNAREs (candidate i-SNAREs) can modulate the activity of fusogenic SNARE complexes, we incorporated candidate i-SNAREs at increasing concentrations into t-SNARE–containing liposomes. (C) Fusion of each type of liposome is compared with control fusion, and is plotted as a function of the molar ratio of the candidate i-SNAREs to the t-SNARE. K50 is the molar ratio of the i-SNARE to the t-SNARE needed to reduce fusion by 50%.

Mentions: To test for i-SNAREs, we examined the effect of increasing amounts of a fifth noncognate Golgi SNARE on fusion mediated by vcis + tcis and by vtrans + ttrans. The fifth SNARE (potential i-SNARE) was added on the t-SNARE side (Fig. 1 B). To compare the relative inhibitory potentials of the i-SNAREs, we establish the K50, i.e., the molar ratio of the i-SNARE to the t-SNARE needed to reduce fusion by 50% (Fig. 1 C).


i-SNAREs: inhibitory SNAREs that fine-tune the specificity of membrane fusion.

Varlamov O, Volchuk A, Rahimian V, Doege CA, Paumet F, Eng WS, Arango N, Parlati F, Ravazzola M, Orci L, Söllner TH, Rothman JE - J. Cell Biol. (2003)

Design of tests for i-SNAREs. (A) The pairing of t-SNAREs composed of one syntaxin heavy chain and two nonsyntaxin light chains with cognate v-SNAREs on the opposite membranes mediates membrane fusion (control fusion). (B) To test whether the presence of additional SNAREs (candidate i-SNAREs) can modulate the activity of fusogenic SNARE complexes, we incorporated candidate i-SNAREs at increasing concentrations into t-SNARE–containing liposomes. (C) Fusion of each type of liposome is compared with control fusion, and is plotted as a function of the molar ratio of the candidate i-SNAREs to the t-SNARE. K50 is the molar ratio of the i-SNARE to the t-SNARE needed to reduce fusion by 50%.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2171956&req=5

fig1: Design of tests for i-SNAREs. (A) The pairing of t-SNAREs composed of one syntaxin heavy chain and two nonsyntaxin light chains with cognate v-SNAREs on the opposite membranes mediates membrane fusion (control fusion). (B) To test whether the presence of additional SNAREs (candidate i-SNAREs) can modulate the activity of fusogenic SNARE complexes, we incorporated candidate i-SNAREs at increasing concentrations into t-SNARE–containing liposomes. (C) Fusion of each type of liposome is compared with control fusion, and is plotted as a function of the molar ratio of the candidate i-SNAREs to the t-SNARE. K50 is the molar ratio of the i-SNARE to the t-SNARE needed to reduce fusion by 50%.
Mentions: To test for i-SNAREs, we examined the effect of increasing amounts of a fifth noncognate Golgi SNARE on fusion mediated by vcis + tcis and by vtrans + ttrans. The fifth SNARE (potential i-SNARE) was added on the t-SNARE side (Fig. 1 B). To compare the relative inhibitory potentials of the i-SNAREs, we establish the K50, i.e., the molar ratio of the i-SNARE to the t-SNARE needed to reduce fusion by 50% (Fig. 1 C).

Bottom Line: A new functional class of SNAREs, designated inhibitory SNAREs (i-SNAREs), is described here.A striking pattern emerges in which certain subunits of the cis-Golgi SNAREpin function as i-SNAREs that inhibit fusion mediated by the trans-Golgi SNAREpin, and vice versa.Although the opposing distributions of the cis- and trans-Golgi SNAREs themselves could provide for a countercurrent fusion pattern in the Golgi stack, the gradients involved would be strongly sharpened by the complementary countercurrent distributions of the i-SNAREs.

View Article: PubMed Central - PubMed

Affiliation: Department of Cellular Biochemistry and Biophysics, Memorial Sloan-Kettering Cancer Center, 1275 York Ave., Box 251, New York, NY 10021, USA.

ABSTRACT
A new functional class of SNAREs, designated inhibitory SNAREs (i-SNAREs), is described here. An i-SNARE inhibits fusion by substituting for or binding to a subunit of a fusogenic SNAREpin to form a nonfusogenic complex. Golgi-localized SNAREs were tested for i-SNARE activity by adding them as a fifth SNARE together with four other SNAREs that mediate Golgi fusion reactions. A striking pattern emerges in which certain subunits of the cis-Golgi SNAREpin function as i-SNAREs that inhibit fusion mediated by the trans-Golgi SNAREpin, and vice versa. Although the opposing distributions of the cis- and trans-Golgi SNAREs themselves could provide for a countercurrent fusion pattern in the Golgi stack, the gradients involved would be strongly sharpened by the complementary countercurrent distributions of the i-SNAREs.

Show MeSH
Related in: MedlinePlus