Ca2+ release mechanisms in cardiac & skeletal muscle
OBJECTIVES• Methodology:
• Chimeric proteins• FRET
• Differences in Ca2+ release between cardiac and skeletal muscle
INTRODUCTION
Ca2+ channel characteristics
Voltage sensitive Ca2+ channel molecular structure
Mammalian Ca2+ channel genes
SR Ca2+ release channel – Ryanodine receptor (RyR)
RyR molecular structure
Mammalian ligand-gated Ca2+ channel genes
DHPR-RyR molecular arrangment
Ca2+ release in skeletal muscle
Ca2+ release in cardiac muscle
DISCUSSION
1.5 nA
15 nA
10 nA
Cardiac sequenceSkeletal muscle sequence
pCac6 (Sk)
pCARD1
pCac6 (Sk)
pCARD1
Ca2+ + 0 / Cd2+
CELL SHORTENING
Cardiac sequenceSkeletal muscle sequence
I II III IV
II-III LOOP
Serine687 to alanine (S687A)Serine – PKA (only in Sk)
I II III IV
II-III LOOP
Dyspedic myotubes
Region with RyR-2 cDNA
injection
Normal myotubes
Dyspedic myotubes with RyR-2
Ca2+ transient during spontaneous contractions
Normal myotubes Dyspedic myotubes with RyR-2
Ca2+ currentRyR-2
expressing Dyspedic myotubes
Ca2+ current & [Ca2+]i
RyR-2 expressing Dyspedic myotubes
Ca2+ currentCSk3
expressing Dyspedic myotubes
Ca2+ transientDyspedic myotubes
Electrically evoked
Spontaneous
Failure (electrical)