Figure 1.

JP2 structure and location in the striated muscle cells. JP2 is located between VDCC and RyRs. JP2 is composed of MORN domains in the N-terminal interacting with the cell membrane, an α-helix domain spanning space, a divergent domain, and a transmembrane domain (TMD) in the C-terminal anchoring JP2 in the SR/ER membrane. PIP-5 kinase and protein kinase sites are in the MORN domains, and calpain cleavage site (AVR565-T566GP) is in the divergent domain. ARR: alanine-rich region; BK: big conductance Ca²⁺-dependent K+ channel; bNLS: bipartite nuclear localization signal-like peptide; CRD: joining region; JP2: junctophilin-2; MORN: membrane occupation and recognition nexus; NLS: monopartite nuclear localization signal; RyR: ryanodine receptor; TM: transmembrane domain; VDCC: voltage-dependent Ca²⁺ channel.