1. Inhibition Of KCa3.1 Channel Is a Potential Novel Therapy for ADPKD
Mamdouh Albaqumi, MD, FASN
Nephrology Section
Department of Medicine
King Faisal Specialist Hospital

2. Mutation in PKD1, PKD2 Leads to ADPKD
Signaling Pathway
Proliferation
Fluid Secretion
Polycystin-1 and polycystin-2 interact to produce calcium-permeable non-selective cation currents dependent upon the heterodimerization of these proteins
at the plasma membrane. It appears, therefore, that the polycystins interaction play a major role in downstream signaling pathway….
Cell-Matrix

3. X X ADPKD Pathogenesis Proliferation Fluid Secretion
In this context, one might think of cysts as unruly "juvenile delinquents", trouble makers nephron segments that never quite reach terminal differentiation and through their uncontrolled growth and increased fluid secretion disrupt the adjacent parenchyma which makes proliferation and fluid secretion a good theraputic targets X X
Proliferation
Fluid Secretion

4. Potential New Therapies
Rapamicin
AVP Antagonist
KCa3.1 Blocker (TRAM-34)

5. Potential New Therapies
Rapamicin
AVP Antagonist
KCa3.1 Blocker (TRAM-34)

6. KCa3.1 Plays a Major Role In Cyst Growth
Na+
H20
KCa3.1 Plays a Major Role In Cyst Growth
Apical Side
(Cyst Lumen)
CFTR Cl
Cl־ Cl
Cl־
cAMP x K+
VPR
KCa3.1
Basolateral Side
ADH

7. Hypothesis
Does KCa3.1 play a role in apical Cl secretion by ADPKD cyst epithelia ?
Could pharmacological inhibition of KCa3.1
be a potential target to slow cyst growth ?

8. Cell Line Madin-Darby canine kidney (MDCK).
Primary human cell cultures were derived from normal regions of nephrectomy specimens (NHK).
Primary human cell cultures were derived from the surface cysts of patients with ADPKD.

9. MDCK, NHK, ADPKD express KCA3.1
Whole Cell
Patch Clamp

10. Forskolin Stimulated Cl- Secretion By The CFTR In ADPKD Cells And Is Inhibited By TRAM-34

11. Direct Activation of KCa3
Direct Activation of KCa3.1 with DCEBIO Stimulates Cl- Current Which is inhibited by Tram-34
CFTR
Cl־ K+ X
KCa3.1
Activates
Tram-34
DCEBIO

12. TRAM-34 Does Not Inhibit Cl- Current (Icl) In MDCK Cells In Which The Basolateral Membrane Is Permeabilized With Nystatin
Low Cl-
Concentration
CFTR
(CFTR Inhibitor)
Cl־
Membrane
Potential: 0 mV K+ X
KCa3.1
Nystatin
Tram-34
High Cl-
Concentration

13. TRAM-34 Inhibits Cyst Growth in Collagen Matrix

14. Both Ca2+ and PI(3)P Are Required For KCa3.1 Channel Activation
Indirectly
PI(3)P
Signal 2 K+ cc K+ K+
Calm K+ 2 3 4 5 6 P OH HO
PI(3)P 1 K+
Ca2+
Signal 1

15. Over Expression Of MTMR6(WT) But Not a MTMR6(PD) Inhibits Cyst Growth By MDCK Cells As Well As Cl- Current
(a) Control
(b) MTMR6(PD)
(c) MTMR6(WT)
No. of systs
Normalized Isc

16. TRAM-34 Blocks Cyst Formation In Embryonic PKD+/- Kidney
Control
Tram34
E13.5, PKD+/-

17. Testing Whether Treatment of PKD-/- Mice with Tram-34 Slows Progression of Kidney Disease
PKD1 (conditional KO) mice
Rapidly develop renal cysts and die Of kidney failure at 3-5 weeks of age.

18. X Slow Progression of Cystic Kidney Disease KCa3.1 -/-
Testing Whether Treatment of PKD-/- Mice Cross Breed With KCa3.1-/- Would Have Less Cystic Kidney X
PKD1 (conditional KO) mice
KCa3.1 -/-
Slow Progression of Cystic Kidney Disease

19. KCa3.1 Inhibitors Are In Phase 3 Clinical Trial For Sickle Cell Disease

20. ACKNOWLEDGEMENTS University of Kansas NYU Darren Wallace
Edward Skolnik
Shekhar Srivastava
Kyung Ko
Zhai Li
Yale
Stevan Somlo
UC Davis
Heike Wulf

21. Thank You