TY - JOUR

T1 - Coding variants identified in patients with diabetes alter PICK1 BAR domain function in insulin granule biogenesis

AU - Andersen, Rita C.

AU - Schmidt, Jan H.

AU - Rombach, Joscha

AU - Lycas, Matthew D.

AU - Christensen, Nikolaj R.

AU - Lund, Viktor K.

AU - Stapleton, Donnie S.

AU - Pedersen, Signe S.

AU - Olsen, Mathias A.

AU - Stoklund, Mikkel

AU - Noes-Holt, Gith

AU - Nielsen, Tommas T.E.

AU - Keller, Mark P.

AU - Jansen, Anna M.

AU - Herlo, Rasmus

AU - Pietropaolo, Massimo

AU - Simonsen, Jens B.

AU - Kjærulff, Ole

AU - Holst, Birgitte

AU - Attie, Alan D.

AU - Gether, Ulrik

AU - Madsen, Kenneth L.

N1 - Publisher Copyright: © 2022 American Society for Clinical Investigation. All rights reserved.

PY - 2022

Y1 - 2022

N2 - Bin/amphiphysin/Rvs (BAR) domains are positively charged crescent-shaped modules that mediate curvature of negatively charged lipid membranes during remodeling processes. The BAR domain proteins PICK1, ICA69, and the arfaptins have recently been demonstrated to coordinate the budding and formation of immature secretory granules (ISGs) at the trans- Golgi network. Here, we identify 4 coding variants in the PICK1 gene from a whole-exome screening of Danish patients with diabetes that each involve a change in positively charged residues in the PICK1 BAR domain. All 4 coding variants failed to rescue insulin content in INS-1E cells upon knock down of endogenous PICK1. Moreover, 2 variants showed dominantnegative properties. In vitro assays addressing BAR domain function suggested that the coding variants compromised BAR domain function but increased the capacity to cause fission of liposomes. Live confocal microscopy and super-resolution microscopy further revealed that PICK1 resides transiently on ISGs before egress via vesicular budding events. Interestingly, this egress of PICK1 was accelerated in the coding variants. We propose that PICK1 assists in or complements the removal of excess membrane and generic membrane trafficking proteins, and possibly also insulin, from ISGs during the maturation process; and that the coding variants may cause premature budding, possibly explaining their dominant-negative function.

AB - Bin/amphiphysin/Rvs (BAR) domains are positively charged crescent-shaped modules that mediate curvature of negatively charged lipid membranes during remodeling processes. The BAR domain proteins PICK1, ICA69, and the arfaptins have recently been demonstrated to coordinate the budding and formation of immature secretory granules (ISGs) at the trans- Golgi network. Here, we identify 4 coding variants in the PICK1 gene from a whole-exome screening of Danish patients with diabetes that each involve a change in positively charged residues in the PICK1 BAR domain. All 4 coding variants failed to rescue insulin content in INS-1E cells upon knock down of endogenous PICK1. Moreover, 2 variants showed dominantnegative properties. In vitro assays addressing BAR domain function suggested that the coding variants compromised BAR domain function but increased the capacity to cause fission of liposomes. Live confocal microscopy and super-resolution microscopy further revealed that PICK1 resides transiently on ISGs before egress via vesicular budding events. Interestingly, this egress of PICK1 was accelerated in the coding variants. We propose that PICK1 assists in or complements the removal of excess membrane and generic membrane trafficking proteins, and possibly also insulin, from ISGs during the maturation process; and that the coding variants may cause premature budding, possibly explaining their dominant-negative function.

U2 - 10.1172/JCI144904

DO - 10.1172/JCI144904

M3 - Journal article

C2 - 35077398

AN - SCOPUS:85125553878

VL - 132

JO - Journal of Clinical Investigation

JF - Journal of Clinical Investigation

SN - 0021-9738

IS - 5

M1 - e144904

ER -