Vol.22 No.2

Original Article

Generation and functional analysis of monoclonal antibodies against the second extracellular loop of human M3 muscarinic acetylcholine receptor

Authors

Hiroto Tsuboi1 , Yumi Nakamura1,2 , Mana Iizuka1 , Naomi Matsuo1 , Isao Matsumoto1 , Takayuki Sumida1

  • Division of Clinical Immunology, Doctoral Programs in Clinical Sciences, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan
  • Japan Society for the Promotion of Science, Tokyo, Japan
Received:

10 June 2011

Accepted:

5 August 2011

Published online:

30 August 2011

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Abstract

The M3 muscarinic acetylcholine receptor (M3R) plays a crucial role in the activation of salivary and lachrymal glands. The M3R contains four extracellular domains (the N-terminal, and the first, second, and third extracellular loops), and we recently detected antibodies against each of these four domains in a subgroup of patients with Sjögren’s syndrome (SS). Functional analysis indicated that the influence of such anti-M3R antibodies on salivary secretion might differ based on the epitopes to which they bind. To clarify the relationship between B-cell epitopes on the M3R and its function, we generated two hybridomas producing anti-M3R monoclonal antibodies against the second extracellular loop of M3R (anti-M3R2nd mAbs) and analyzed their function by Ca2+-influx assays, using a human salivary gland (HSG) cell line. These two anti-M3R2nd mAbs suppressed Ca2+-influx in the HSG cells induced by cevimeline stimulation, suggesting that autoantibodies against the second extracellular loop of M3R could be involved in salivary dysfunction in patients with SS.

Key words

Autoantibodies - Ca2+-influx - M3 muscarinic acetylcholine receptor - Salivary secretion - Sjögren’s syndrome