SORBS1
CAP/Ponsin, also known as Sorbin and SH3 domain-containing protein 1, is made by the human SORBS1 gene. It’s part of a small family of adaptor proteins that help connect signals from outside the cell to the inside and organize the cell’s cytoskeleton. Other family members include ArgBP2 and vinexin. CAP/Ponsin contains a conserved SOHO domain and three SH3 domains and can be produced as about 13 different forms, ranging from 81 to 142 kDa.
Where it’s found: CAP/Ponsin is mainly expressed in the heart, skeletal muscle, liver, fat (adipose) tissue, and macrophages.
What it does: In muscle, CAP/Ponsin helps form mature costameres, the connections between muscle fibers and the surrounding matrix. Too much CAP/Ponsin can disrupt normal cell–matrix contacts. It also plays a role in insulin signaling and glucose uptake by helping recruit components to lipid raft signaling complexes, which enhances insulin signaling.
In mice, CAP/Ponsin in macrophages influences inflammation and insulin resistance: lacking SORBS1 in macrophages can protect against high-fat diet–induced insulin resistance and reduce inflammation. In non-muscle cells, CAP/Ponsin can limit cell spreading and turnover of focal adhesions; reducing CAP/Ponsin can boost certain signaling pathways (like PAK/MEK/ERK) and cell migration.
Clinical notes: CAP/Ponsin levels are reduced in end-stage heart failure but can improve with mechanical unloading of the heart. A variation in SORBS1 has been linked to type 2 diabetes and obesity.
Interactions: SORBS1 interacts with multiple signaling proteins, helping to coordinate cellular responses.
This page was last edited on 2 February 2026, at 00:42 (CET).