title: Claudin-4 is required for AMPK-modulated paracellular permeability in submandibular gland cells.
abstract: Tight junction plays an important role in mediating paracellular permeability in epithelia. We previously found that activation of AMP-activated protein kinase (AMPK) increased saliva secretion by modulating paracellular permeability in submandibular glands. However, the molecular mechanisms underlying AMPK-modulated paracellular permeability are unknown. In this study, we found that AICAR, an AMPK agonist, increased saliva secretion in the isolated rat submandibular glands, decreased transepithelial electrical resistance (TER), and increased 4 kDa FITC-dextran flux in cultured SMG-C6 cells. AICAR also induced redistribution of tight junction protein claudin-4, but not claudin-1, claudin-3, occludin, or ZO-1, from the cytoplasm to the membrane. Moreover, knockdown of claudin-4 by shRNA suppressed while claudin-4 re-expression restored the TER and 4 kDa FITC-dextran flux responses to AICAR. Additionally, AICAR increased ERK1/2 phosphorylation, and inhibition of ERK1/2 by U0126, an ERK1/2 kinase inhibitor, or by siRNA decreased AICAR-induced TER responses. AICAR induced the serine S199 phosphorylation of claudin-4 and enhanced the interaction of claudin-4 and occludin. Furthermore, pretreatment with U0126 significantly suppressed AMPK-modulated phosphorylation, redistribution, and interaction with occludin of claudin-4. Taken together, these results indicated that claudin-4 played a crucial role in AMPK-modulated paracellular permeability and ERK1/2 was required in AMPK-modulated tight junction barrier function in submandibular gland.
authors.affiliation: Center for Salivary Gland Diseases of Peking University School and Hospital of Stomatology, Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University Health Science Center and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing 100191, China.
authors.forename: Ruo-Lan
authors.initials: RL
authors.lastname: Xiang
authors.affiliation: Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Mei
authors.initials: M
authors.lastname: Mei
authors.affiliation: Center for Salivary Gland Diseases of Peking University School and Hospital of Stomatology, Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University Health Science Center and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing 100191, China.
authors.forename: Xin
authors.initials: X
authors.lastname: Cong
authors.affiliation: Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: Center for Salivary Gland Diseases of Peking University School and Hospital of Stomatology, Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University Health Science Center and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing 100191, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Central Laboratory, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Chong
authors.initials: C
authors.lastname: Ding
authors.affiliation: Center for Salivary Gland Diseases of Peking University School and Hospital of Stomatology, Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Peking University Health Science Center and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Beijing 100191, China pathophy@bjmu.edu.cn gyyu@263.net.
authors.forename: Li-Ling
authors.initials: LL
authors.lastname: Wu
authors.affiliation: Department of Oral and Maxillofacial Surgery, Peking University School and Hospital of Stomatology, Beijing 100081, China pathophy@bjmu.edu.cn gyyu@263.net.
authors.forename: Guang-Yan
authors.initials: GY
authors.lastname: Yu
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000378:metabolism*; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000378:metabolism; D000818:Animals; D002070:Butadienes / Q000494:pharmacology; D002460:Cell Line; D062506:Claudin-4 / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D062793:Occludin / Q000378:metabolism; D010539:Permeability / Q000187:drug effects; D051381:Rats; D012265:Ribonucleotides / Q000378:metabolism; D013363:Submandibular Gland / Q000166:cytology / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein / Q000378:metabolism
chemical_list: D002070:Butadienes; D062506:Claudin-4; D004791:Enzyme Inhibitors; D009570:Nitriles; D062793:Occludin; C568987:Ocln protein, rat; D012265:Ribonucleotides; C569044:Tjp1 protein, rat; C113580:U 0126; D062826:Zonula Occludens-1 Protein; D000620:Aminoimidazole Carboxamide; D048052:Mitogen-Activated Protein Kinase 3; D055372:AMP-Activated Protein Kinases; C031143:AICA ribonucleotide
keywords: AMP-activated protein kinase; claudin-4; paracellular permeability; submandibular gland; tight junction