unc-89 Antibody
Description
Definition and Target
The UNC-89 antibody specifically recognizes UNC-89, a multi-domain protein localized to the M-line of muscle sarcomeres. UNC-89 is required for sarcomere organization, thick filament alignment, and calcium signaling in both body wall and pharyngeal muscles . The antibody enables visualization and functional analysis of UNC-89 isoforms, which range from 156 kDa to 900 kDa and include two protein kinase domains (PK1 and PK2), immunoglobulin (Ig) domains, fibronectin type 3 (Fn3) domains, and signaling modules (SH3, DH, PH) .
Key Research Applications
The UNC-89 antibody has been instrumental in:
-
Localizing UNC-89 to the M-line: Immunostaining reveals UNC-89’s striated pattern in body wall muscle, consistent with its role in sarcomere maintenance .
-
Studying Sarcomere Disorganization: In unc-89 mutants, the antibody highlights disrupted myosin (MHC-A) and sarcoplasmic reticulum (SERCA) organization, linking UNC-89 to sarcomere integrity .
-
Analyzing Calcium Signaling: Reduced calcium transient amplitudes in unc-89 mutants, detected via YC3.60 calcium sensors, correlate with disorganized SERCA and ryanodine receptors (RyRs) .
Role in Sarcomere Maintenance
-
Developmental Defects: While unc-89 mutants show normal sarcomeres in larvae, adults exhibit severe disorganization of A-bands and M-lines . Antibody staining confirms UNC-89’s necessity for maintaining sarcomere architecture during muscle growth .
-
Interaction with Paramyosin: The SH3 domain of UNC-89 binds paramyosin, a thick filament component, suggesting a direct role in filament alignment .
Calcium Mobilization
-
Reduced Calcium Peaks: unc-89 mutants exhibit 30–40% lower peak calcium levels in pharyngeal and body wall muscles, as shown by YC3.60 imaging .
-
Delayed Activation: Calcium rise times are prolonged in mutants, indicating impaired excitation-contraction coupling .
Genetic Interactions
-
Synergy with Ion Channels: Double mutants of unc-89 with unc-68 (RyR) or egl-19 (L-type Ca²⁺ channel) show exacerbated locomotion defects, emphasizing UNC-89’s role in calcium handling .
Technical Considerations
-
Specificity: The antibody detects large UNC-89 isoforms (e.g., UNC-89-B and UNC-89-F) but may not recognize smaller isoforms lacking epitopes in the interkinase region .
-
Limitations: Epitope mapping remains incomplete, and Western blot performance varies due to UNC-89’s extreme size (>8,000 residues) .
Product Specs
Constituents: 50% Glycerol, 0.01M PBS, pH 7.4
Target Background
UNC-89 is a structural component of the muscle M line, playing a crucial role in the assembly and organization of sarcomere myofilaments. The large isoforms (a, b, d, and f) are essential for maintaining the organization of sarcomeres during body wall muscle development, while the smaller isoforms (c and d) have a minor role. Isoforms b and f are particularly important for the organization of unc-15/paramyosin into sarcomere thick filaments in body wall muscles. UNC-89 regulates the organization of myosin thick filaments by binding to mel-26, a substrate adapter of the cul-3 E3 ubiquitin-protein ligase complex, preventing the degradation of the microtubule severing protein mei-1.
UNC-89 also acts as a guanine nucleotide exchange factor (GEF) for the Rho GTPase rho-1, but not for ced-10, mig-2, and cdc-42. The large isoforms further regulate Ca(2+) signaling during muscle contraction by ensuring the correct localization of sarco-endoplamic reticulum Ca(2+) ATPase sca-1 and ryanodine receptor unc-68. By controlling the contraction and/or organization of pharyngeal muscles, UNC-89 plays a role in the formation of pharyngeal gland cell extension.
- Studies have shown that the level of MEI-1 protein is reduced in an unc-89 mutant, suggesting that UNC-89 normally inhibits the CUL-3/MEL-26 complex toward MEI-1 in striated muscle. (PMID: 22621901)
- Data indicates that UNC-89 is involved in maintaining muscle cell architecture, and this precise organization is crucial for optimal calcium mobilization and efficient muscle contraction. (PMID: 22768340)
- Research reveals that the coding sequence for unc-89 is larger than previously thought and encodes at least four major isoforms. (PMID: 15313609)
- Yeast two-hybrid screening using a portion of UNC-89, including PK2, identified SCPL-1 (small CTD phosphatase-like-1), which contains a C terminal domain (CTD) phosphatase type domain. (PMID: 18337465)
- Findings support a model where the DH-PH region of UNC-89 activates RHO-1 GTPase for the organization of myosin filaments in C. elegans muscle cells. (PMID: 18801371)
- SCPL-1 interacts with LIM-9 (FHL), a protein previously identified as an interactor of UNC-97 (PINCH) and UNC-96, components of an M-line costamere in nematode muscle. (PMID: 19244614)
