PMID- 25602367 OWN - NLM STAT- MEDLINE DCOM- 20151026 LR - 20150317 IS - 1879-1611 (Electronic) IS - 0022-1910 (Linking) VI - 73 DP - 2015 Feb TI - Ca2+ and endoplasmic reticulum Ca2+-ATPase regulate the formation of silk fibers with favorable mechanical properties. PG - 53-9 LID - S0022-1910(15)00004-9 [pii] LID - 10.1016/j.jinsphys.2015.01.002 [doi] AB - Calcium ions (Ca(2+)) are crucial for the conformational transition of silk fibroin in vitro, and silk fibroin conformations correlate with the mechanical properties of silk fibers. To investigate the relationship between Ca(2+) and mechanical properties of silk fibers, CaCl2 was injected into silkworms (Bombyx mori). Fourier-transform infrared spectroscopy (FTIR) analysis and mechanical testing revealed that injection of CaCl2 solution (7.5mg/g body weight) significantly increased the levels of alpha-helix and random coil structures of silk proteins. In addition, extension of silk fibers increased after CaCl2 injection. In mammals, sarcoplasmic reticulum Ca(2+)-ATPase in muscle and endoplasmic reticulum Ca(2+)-ATPase in other tissues (together denoted by SERCA) are responsible for calcium balance. Therefore, we analyzed the expression pattern of silkworm SERCA (BmSERCA) in silk glands and found that BmSERCA was abundant in the anterior silk gland (ASG). After injection of thapsigargin (TG) to block SERCA activity, silkworms showed a silk-spinning deficiency and their cocoons had higher calcium content compared to that of controls. Moreover, FTIR analysis revealed that the levels of alpha-helix and beta-sheet structures increased in silk fibers from TG-injected silkworms compared to controls. The results provide evidence that BmSERCA has a key function in calcium transportation in ASG that is related to maintaining a suitable ionic environment. This ionic environment with a proper Ca(2+) concentration is crucial for the formation of silk fibers with favorable mechanical performances. CI - Copyright (c) 2015 Elsevier Ltd. All rights reserved. FAU - Wang, Xin AU - Wang X AD - State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China. Electronic address: wangxin3@swu.edu.cn. FAU - Li, Yi AU - Li Y AD - State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China. Electronic address: liy7raul@swu.edu.cn. FAU - Xie, Kang AU - Xie K AD - State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China. Electronic address: xiekanglwdd@163.com. FAU - Yi, Qiying AU - Yi Q AD - Animal Center, Chongqing Medical University, Chongqing 400016, China. Electronic address: yiqiying_2011@yahoo.com. FAU - Chen, Quanmei AU - Chen Q AD - State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China. Electronic address: eidoloncqm@126.com. FAU - Wang, Xiaohuan AU - Wang X AD - State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China. Electronic address: wangxiaohuan1024@126.com. FAU - Shen, Hong AU - Shen H AD - College of Resources and Environments, Southwest University, Chongqing 400716, China. Electronic address: shenhong@swu.edu.cn. FAU - Xia, Qingyou AU - Xia Q AD - State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China. Electronic address: xiaqy@swu.edu.cn. FAU - Zhao, Ping AU - Zhao P AD - State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400716, China. Electronic address: zhaop@swu.edu.cn. LA - eng PT - Journal Article PT - Research Support, Non-U.S. Gov't DEP - 20150117 PL - England TA - J Insect Physiol JT - Journal of insect physiology JID - 2985080R RN - 0 (Silk) RN - EC 3.6.3.8 (Sarcoplasmic Reticulum Calcium-Transporting ATPases) RN - M4I0D6VV5M (Calcium Chloride) RN - SY7Q814VUP (Calcium) SB - IM MH - Animals MH - Bombyx/*metabolism MH - Calcium/*metabolism MH - Calcium Chloride/metabolism MH - Mechanical Phenomena MH - Protein Structure, Secondary MH - Sarcoplasmic Reticulum Calcium-Transporting ATPases/*metabolism MH - Silk/biosynthesis/*chemistry MH - Spectroscopy, Fourier Transform Infrared OTO - NOTNLM OT - Calcium ion OT - Endoplasmic reticulum Ca(2+)-ATPase OT - FTIR OT - Mechanical properties OT - Silk fibers EDAT- 2015/01/21 06:00 MHDA- 2015/10/27 06:00 CRDT- 2015/01/21 06:00 PHST- 2014/08/26 00:00 [received] PHST- 2015/01/08 00:00 [revised] PHST- 2015/01/09 00:00 [accepted] PHST- 2015/01/21 06:00 [entrez] PHST- 2015/01/21 06:00 [pubmed] PHST- 2015/10/27 06:00 [medline] AID - S0022-1910(15)00004-9 [pii] AID - 10.1016/j.jinsphys.2015.01.002 [doi] PST - ppublish SO - J Insect Physiol. 2015 Feb;73:53-9. doi: 10.1016/j.jinsphys.2015.01.002. Epub 2015 Jan 17.