WNK1 is a novel regulator of Munc18c-syntaxin 4 complex formation in soluble NSF attachment protein receptor (SNARE)-mediated vesicle exocytosis

Eunjin Oh, Charles J. Heise, Jessie M. English, Melanie H. Cobb, Debbie C. Thurmond

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

Defects in soluble NSF attachment protein receptor (SNARE)-mediated granule exocytosis occur in islet beta cells, adipocytes, and/or skeletal muscle cells correlate with increased susceptibility to insulin resistance and diabetes. The serine/threonine kinase WNK1 (with no K (lysine)) has recently been implicated in exocytosis and is expressed in all three of these cell types. To search for WNK1 substrates related to exocytosis, we conducted a WNK1 two-hybrid screen, which yielded Munc18c. Munc18c is known to be a key regulator of accessibility of the target membrane (t-SNARE) protein syntaxin 4 to participate in SNARE core complex assembly, although a paucity of Munc18c-binding factors has precluded discovery of its precise functions. To validate WNK1 as a new Munc18c-interacting partner, the direct interaction between WNK1 and Munc18c was confirmed using in vitro binding analysis, and endogenous WNK1-Munc18c complexes were detected in the cytosolic and plasma membrane compartments of the islet beta cell line MIN6. This binding interaction is mediated through the N-terminal 172 residues of Munc18c and the kinase domain residues of WNK1 (residues 159-491). Expression of either of these two minimal interaction domains resulted in inhibition of glucose-stimulated insulin secretion, consistent with a functional importance for the endogenous WNK1-Munc18c complex in exocytosis. Interestingly, Munc18c failed to serve as a WNK1 substrate in kinase activity assays, suggesting that WNK1 functions in SNARE complex assembly outside its role as a kinase. Taken together, these data support a novel role for WNK1 and a new mechanism for the regulation of SNARE complex assembly by WNK1-Munc18c complexes.

Original languageEnglish
Pages (from-to)32613-32622
Number of pages10
JournalJournal of Biological Chemistry
Volume282
Issue number45
DOIs
StatePublished - Nov 9 2007

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Soluble N-Ethylmaleimide-Sensitive Factor Attachment Proteins
Qa-SNARE Proteins
SNARE Proteins
Exocytosis
Phosphotransferases
Islets of Langerhans
Cells
Insulin
Protein-Serine-Threonine Kinases
Substrates
Cell membranes
Medical problems
Adipocytes
Muscle Cells
Lysine
Muscle
Insulin Resistance
Assays
Skeletal Muscle
Cell Membrane

ASJC Scopus subject areas

  • Biochemistry

Cite this

WNK1 is a novel regulator of Munc18c-syntaxin 4 complex formation in soluble NSF attachment protein receptor (SNARE)-mediated vesicle exocytosis. / Oh, Eunjin; Heise, Charles J.; English, Jessie M.; Cobb, Melanie H.; Thurmond, Debbie C.

In: Journal of Biological Chemistry, Vol. 282, No. 45, 09.11.2007, p. 32613-32622.

Research output: Contribution to journalArticle

Oh, Eunjin ; Heise, Charles J. ; English, Jessie M. ; Cobb, Melanie H. ; Thurmond, Debbie C. / WNK1 is a novel regulator of Munc18c-syntaxin 4 complex formation in soluble NSF attachment protein receptor (SNARE)-mediated vesicle exocytosis. In: Journal of Biological Chemistry. 2007 ; Vol. 282, No. 45. pp. 32613-32622.
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