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Stretch‐induced TRPC4 downregulation in RASM cells may be due to changes in intracellular calcium
Author(s) -
Hoffmann Sarah E,
Kuriakose Marella,
SonguMize Emel
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1115-d
Subject(s) - downregulation and upregulation , cytosol , chemistry , nifedipine , microbiology and biotechnology , intracellular , calcium , biophysics , biochemistry , biology , enzyme , gene , organic chemistry
Our previous work showed that cyclic stretch significantly decreases TRPC4 expression in rat aortic smooth muscle (RASM) cells and is prevented by CPA. TRPC4 downregulation may be a compensatory mechanism to reduce increased [Ca 2+ ] SR resulting from entry through stretch‐activated channels. However, we do not yet know the role of cytosolic Ca 2+ . We hypothesized that TRPC4 downregulation may also serve to reduce stretch‐induced increases in cytosolic [Ca 2+ ] and outlined the following aims: (1) demonstrate that increased cytosolic [Ca 2+ ] in the absence of stretch can decrease TRPC4 protein expression, and (2) establish whether blocking Ca 2+ entry into the cytosol can prevent stretch‐induced TRPC4 downregulation. RASM cells were subjected to cyclic stretch for 6h using the Flexercell Strain Unit FX‐4000. Control cells were not stretched. To address Aim (1), the [Ca 2+ ] of the cell culture medium was increased to 10 mM in both stretch and non‐stretch conditions, and TRPC4 expression was measured by Western blot. 10 mM Ca 2+ decreased TRPC4 protein expression in the absence of stretch (p<0.05). However, high Ca 2+ conditions in the presence of stretch did not show any additional downregulation. To address Aim (2), gadolinium was added before mechanical strain to block stretch‐activated channels. Nifedipine was used to assess the contribution of L‐type channels. Addition of either drug in the absence of stretch increased TRPC4 expression. However, stretch‐induced downregulation was still present within each drug condition. These results suggest that TRPC4 proteins may play an important role in stabilizing Ca 2+ levels in RASM cells during mechanical or pharmacological changes. Support: COBRE P20 RR18766 “Mentoring in Cardiovascular Biology”