TY - JOUR
T1 - Ca2+-dependent inhibition of Na+/H+ exchanger 3 (NHE3) requires an NHE3-E3KARP-α-actinin-4 complex for oligomerization and endocytosis
AU - Kim, Jae Ho
AU - Lee-Kwon, Whaseon
AU - Park, Jong Bae
AU - Ryu, Sung Ho
AU - Chris Yun, C. H.
AU - Donowitz, Mark
PY - 2002/6/28
Y1 - 2002/6/28
N2 - Two PDZ domain-containing proteins, NHERF and E3KARP are necessary for cAMP-dependent inhibition of Na+/H+ exchanger 3 (NHE3). In this study, we demonstrate a specific role of E3KARP, which is not duplicated by NHERF, in Ca2+-dependent inhibition of NHE3 activity. NHE3 activity is inhibited by elevation of intracellular Ca2+ ([Ca2+]i) in PS120 fibroblasts stably expressing E3KARP but not those expressing NHERF. In addition, this Ca2+-dependent inhibition requires Ca2+-dependent association between α-actinin-4 and E3KARP. NHE3 is indirectly connected to α-actinin-4 in a protein complex through Ca2+-dependent interaction between α-actinin-4 and E3KARP, which occurs through the actin-binding domain plus spectrin repeat domain of α-actinin-4. Elevation of [Ca2+]i results in oligomerization and endocytosis of NHE3 as well as in inhibition of NHE3 activity. Over-expression of α-actinin-4 potentiates the inhibitory effect of ionomycin on NHE3 activity by accelerating the oligomerization and endocytosis of NHE3. In contrast, overexpression of the actin-binding domain plus spectrin repeat domain acts as a dominant-negative mutant and prevents the inhibitory effect of ionomycin on NHE3 activity as well as the oligomerization and internalization of NHE3. From these results, we propose that elevated Ca2+ inhibits NHE3 activity through oligomerization and endocytosis of NHE3, which occurs via formation of an NHE3-E3KARP-α-actinin-4 complex.
AB - Two PDZ domain-containing proteins, NHERF and E3KARP are necessary for cAMP-dependent inhibition of Na+/H+ exchanger 3 (NHE3). In this study, we demonstrate a specific role of E3KARP, which is not duplicated by NHERF, in Ca2+-dependent inhibition of NHE3 activity. NHE3 activity is inhibited by elevation of intracellular Ca2+ ([Ca2+]i) in PS120 fibroblasts stably expressing E3KARP but not those expressing NHERF. In addition, this Ca2+-dependent inhibition requires Ca2+-dependent association between α-actinin-4 and E3KARP. NHE3 is indirectly connected to α-actinin-4 in a protein complex through Ca2+-dependent interaction between α-actinin-4 and E3KARP, which occurs through the actin-binding domain plus spectrin repeat domain of α-actinin-4. Elevation of [Ca2+]i results in oligomerization and endocytosis of NHE3 as well as in inhibition of NHE3 activity. Over-expression of α-actinin-4 potentiates the inhibitory effect of ionomycin on NHE3 activity by accelerating the oligomerization and endocytosis of NHE3. In contrast, overexpression of the actin-binding domain plus spectrin repeat domain acts as a dominant-negative mutant and prevents the inhibitory effect of ionomycin on NHE3 activity as well as the oligomerization and internalization of NHE3. From these results, we propose that elevated Ca2+ inhibits NHE3 activity through oligomerization and endocytosis of NHE3, which occurs via formation of an NHE3-E3KARP-α-actinin-4 complex.
UR - http://www.scopus.com/inward/record.url?scp=0037189512&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0037189512&partnerID=8YFLogxK
U2 - 10.1074/jbc.M200835200
DO - 10.1074/jbc.M200835200
M3 - Article
C2 - 11948184
AN - SCOPUS:0037189512
SN - 0021-9258
VL - 277
SP - 23714
EP - 23724
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 26
ER -