
-   The expression of cardiac ANKRD1 is rapidly increased in response to various hypertrophic stimuli including pressure overload and mechanical stress [PMID: 10904011]. CARP contains within its ankyrin repeat region a binding site for the myofibrillar elastic protein titin. CARP co-localizes with I-band titin N2A epitopes in adult heart muscle tissues. Studies indicate that the myofibrillar CARP are regulated by stretch, and that this links titin-N2A-based myofibrillar stress/strain signals to a CARP-based regulation of muscle gene expression [PMID: 14583192].
-   A new pathway encompassing calpain 3 and its substrate CARP is involved in the regulation of the nuclear factor-kappaB pathway in skeletal muscle. Cleavage of ANKRD1 by calpain may possibly affect the nuclear import of ANKRD1 and hence affect its downstream gene expression regulatory functions [PMID: 20860623].
-   CARP can negatively regulate an HF-1-TK minimal promoter in an HF-1 sequence-dependent manner in cardiac myocytes, and CARP displays a transcriptional inhibitory activity when fused to a GAL4 DNA-binding domain in both cardiac and noncardiac cell context [PMID: 9043061].

## Summary

Ankrd1, coding for the CARP protein, plays a crucial role in maintaining skeletal muscle integrity and responding to stress [CS: 9]. When skeletal muscles undergo pathological remodeling or face high resistance contractions, as in muscular dystrophies or intense exercise, there is an upregulation of CARP mRNA [CS: 8]. Studies suggest that effect of CARP may act as a nuclear transcription factor that negatively regulates the expression of cardiac genes [CS: 5]. CARP also interacts with key structural proteins like myopalladin and titin in muscle tissues, which are critical for maintaining the structural integrity of muscle fibers [CS: 9].
