Molecular interactions of the junctional foot protein and dihydropyridine receptor in skeletal muscle triads

Abstract

Isolated triadic proteins were employed to investigate the molecular architecture of the triad junction in skeletal muscle. Immunoaffinity-purified junctional foot protein (JFP), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), aldolase and partially purified dihydropyridine (DHP) receptor were employed to probe protein-protein interactions using affinity chromatography, protein overlay and crosslinking techniques. The JFP, an integral protein of the sarcoplasmic reticulum (SR) preferentially binds to GAPDH and aldolase, peripheral proteins of the transverse (T)-tubule. No direct binding of JFP to the DHP receptor was detected. The interactions of JFP with GAPDH and aldolase appear to be specific since other glycolytic enzymes associated with membranes do not bind to the JFP. The DHP receptor, an integral protein of the T-tubule, also binds GAPDH and aldolase. A ternary complex between the JFP and the DHP receptor can be formed in the presence of GAPDH. In addition, the DHP receptor binds to a previously undetected Mr 95 K protein which is distinct from the SR Ca2+ pump and phosphorylase b. The Mr 95 K protein is an integral protein of the junctional domain of the SR terminal cisternae. It is also present in the newly identified "strong triads" (accompanying paper). From these findings, we propose a new model for the triad junction.

The Muscle-specific Calmodulin-dependent Protein Kinase Assembles with the Glycolytic Enzyme Complex at the Sarcoplasmic Reticulum and Modulates the Activity of Glyceraldehyde-3-phosphate Dehydrogenase in a Ca2+/Calmodulin-dependent Manner

“…Furthermore, the data indicate that CaMKII␤ M can interact with GAPDH to phosphorylate and modulate its activity in a Ca 2ϩ -and CaM-dependent manner. GAPDH was found to be distributed in muscle cytosol and the SR membrane, and ultrastructural localization studies have also revealed that GAPDH along with other glycolytic enzymes are bound to the cytoplasmic face of the SR membrane in skeletal muscle (33,38). A role for GAPDH together with 3-phosphoglycerate kinase (PGK) has been previously established in the production of ATP from GAP, NAD ϩ , P i , and ADP at the level of the SR membrane (19,20,39,40).…”

Triadin Binding to the C-Terminal Luminal Loop of the Ryanodine Receptor is Important for Skeletal Muscle Excitation–Contraction Coupling

“…Triadin is a junctional SR protein discovered in 1990 by Brandt et al (1990) that was originally proposed to play a critical role in excitation-contraction (EC) coupling (Kim et al, 1990). However, since the bulk of the protein is located within the SR lumen where it binds to CSQ and the RyR (Knudson et al, 1993b;Guo and Campbell, 1995), it is currently believed to facilitate cross-talk between CSQ and the RyR (Beard et al, 2002), rather than directly infl uence EC coupling (Gyorke et al, 2004).…”

Effects of anti‐triadin antibody on Ca2+ release from sarcoplasmic reticulum

“…Recently som~ of us have presented evidence that triadin is a major constituent of the triad junction which binds both to the DHP receptor and the JFP [11,12]. This protein is an intrinsic protein of the terminal cisternae (TC) with a distribution and content approximately the same as those of the J FP [13].…”