Rho-ROCK signal pathway regulates microtubule-based process formation of cultured podocytes--inhibition of ROCK promoted process elongation.
BACKGROUND
Podocytes, renal glomerular visceral epithelial cells, have two kinds of processes, namely major processes containing microtubules (MTs) and foot processes with actin filaments (AFs). The present study investigated how MTs are organized by the Rho-ROCK signal transduction pathway during process formation of podocytes.


METHODS
After induction of differentiation, podocytes of the conditionally immortalized mouse cell line were treated with Y-27632, a specific inhibitor of ROCK, and exoenzyme C3, an inhibitor of RhoA, as well as with forskolin whose effects include inhibition of RhoA, in order to inhibit the Rho-ROCK pathway.


RESULTS
Inhibition of ROCK significantly enhanced the formation of thick processes containing MT bundles. Y-27632 promoted process formation even in the presence of latrunculin A which disrupts AFs, strongly suggesting that ROCK directly regulates MT assembly. Treatment with Y-27632 increased MT stability, and stabilized MTs preferentially localized in podocyte processes. Moreover, when treated with a combination of Y-27632 and forskolin, and with Y-27632 and C3 as well, podocytes developed not only MT-based thick processes but also AF-based thin projections.


CONCLUSIONS
These data indicate a contribution of ROCK in MT organization to promote podocyte process formation, although it was originally thought to regulate AF assembly. AF-based thin projections seem to be induced mainly by inhibition of RhoA and ROCK. The present study reveals a significant role of the Rho-ROCK signal pathway in the reorganization of both MTs and AFs during process formation of podocytes.
Gao
Shuang-Yan
SY
Department of Anatomy and Embryology, Integrated Center for Science, Ehime University, Ehime, Japan.
Li
Chun-Yu
CY
Chen
Jie
J
Pan
Lei
L
Saito
Shouichiro
S
Terashita
Takehiro
T
Saito
Kyoko
K
Miyawaki
Kyojy
K
Shigemoto
Kazuhiro
K
Mominoki
Katsumi
K
Matsuda
Seiji
S
Kobayashi
Naoto
N
D036002:ADP Ribose Transferases / Q000494:pharmacology; D000107:Acetylation; D008841:Actin Cytoskeleton / Q000378:metabolism; D000199:Actins / Q000378:metabolism; D000209:Acute-Phase Proteins / Q000378:metabolism*; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001905:Botulinum Toxins / Q000494:pharmacology; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D003599:Cytoskeleton / Q000201:enzymology / Q000378:metabolism; D022001:Focal Adhesions / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D007678:Kidney Glomerulus / Q000166:cytology / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D051379:Mice; D008870:Microtubules / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology*; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines; D014404:Tubulin / Q000737:chemistry / Q000378:metabolism; D054460:rho-Associated Kinases
D000199:Actins; D000209:Acute-Phase Proteins; D000577:Amides; D019086:Bridged Bicyclo Compounds, Heterocyclic; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; D013844:Thiazoles; D053778:Thiazolidines; D014404:Tubulin; C010781:acute-phase protein rho; C108830:Y 27632; D005576:Colforsin; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D001905:Botulinum Toxins; C037067:latrunculin A