TY - JOUR
T1 - Downregulation of TRPC6 protein expression by high glucose, a possible mechanism for the impaired Ca2+ signaling in glomerular mesangial cells in diabetes
AU - Graham, Sarabeth
AU - Ding, Min
AU - Sours-Brothers, Sherry
AU - Yorio, Thomas
AU - Ma, Jian Xing
AU - Ma, Rong
PY - 2007/10
Y1 - 2007/10
N2 - The present study was performed to investigate whether transient receptor potential (TRPC)6 participated in Ca2+ signaling of glomerular mesangial cells (MCs) and expression of this protein was altered in diabetes. Western blots and real-time PCR were used to evaluate the expression level of TRPC6 protein and mRNA, respectively. Cell-attached patch-clamp and fura-2 fluorescence measurements were utilized to assess angiotensin II (ANG II)-stimulated membrane currents and Ca2+ responses in MCs. In cultured human MCs, high glucose significantly reduced expression of TRPC6 protein, but there was no effect on either TRPC1 or TRPC3. The high glucose-induced effect on TRPC6 was time and dose dependent with the maximum effect observed on day 7 and at 30 mM glucose, respectively. In glomeruli isolated from streptozotocin-induced diabetic rats, TRPC6, but not TRPC1, was markedly reduced compared with the glomeruli of control rats. Furthermore, TRPC6 mRNA in MCs was also significantly decreased by high glucose as early as 1 day after treatment with maximal reduction on day 4. Patch-clamp experiments showed that ANG II-stimulated membrane currents in MCs were significantly attenuated or enhanced by knockdown or overexpression of TRPC6, respectively. Fura-2 fluorescence measurements revealed that the ANG II-induced Ca2+ influxes were markedly inhibited in MCs with TRPC6 knockdown, reminiscent of the impaired Ca2+ entry in response to ANG II in high glucose-treated MCs. These results suggest that the TRPC6 protein expression in MCs was downregulated by high glucose and the deficiency of TRPC6 protein might contribute to the impaired Ca2+ signaling of MCs seen in diabetes.
AB - The present study was performed to investigate whether transient receptor potential (TRPC)6 participated in Ca2+ signaling of glomerular mesangial cells (MCs) and expression of this protein was altered in diabetes. Western blots and real-time PCR were used to evaluate the expression level of TRPC6 protein and mRNA, respectively. Cell-attached patch-clamp and fura-2 fluorescence measurements were utilized to assess angiotensin II (ANG II)-stimulated membrane currents and Ca2+ responses in MCs. In cultured human MCs, high glucose significantly reduced expression of TRPC6 protein, but there was no effect on either TRPC1 or TRPC3. The high glucose-induced effect on TRPC6 was time and dose dependent with the maximum effect observed on day 7 and at 30 mM glucose, respectively. In glomeruli isolated from streptozotocin-induced diabetic rats, TRPC6, but not TRPC1, was markedly reduced compared with the glomeruli of control rats. Furthermore, TRPC6 mRNA in MCs was also significantly decreased by high glucose as early as 1 day after treatment with maximal reduction on day 4. Patch-clamp experiments showed that ANG II-stimulated membrane currents in MCs were significantly attenuated or enhanced by knockdown or overexpression of TRPC6, respectively. Fura-2 fluorescence measurements revealed that the ANG II-induced Ca2+ influxes were markedly inhibited in MCs with TRPC6 knockdown, reminiscent of the impaired Ca2+ entry in response to ANG II in high glucose-treated MCs. These results suggest that the TRPC6 protein expression in MCs was downregulated by high glucose and the deficiency of TRPC6 protein might contribute to the impaired Ca2+ signaling of MCs seen in diabetes.
KW - Ca influxes
KW - Diabetic nephropathy
KW - Glomeruli
KW - Hyperfiltration
UR - http://www.scopus.com/inward/record.url?scp=35348856319&partnerID=8YFLogxK
U2 - 10.1152/ajprenal.00185.2007
DO - 10.1152/ajprenal.00185.2007
M3 - Article
C2 - 17699555
AN - SCOPUS:35348856319
SN - 0363-6127
VL - 293
SP - F1381-F1390
JO - American Journal of Physiology - Renal Physiology
JF - American Journal of Physiology - Renal Physiology
IS - 4
ER -