Secretory carrier-associated membrane protein 5 regulates cell-surface targeting of T-type calcium channels

ABSTRACT

Missense mutations in the human secretary carrier-associated membrane protein 5 (SCAMP5) cause a variety of neurological disorders including neurodevelopmental delay, epilepsy, and Parkinson’s disease. We recently documented the importance of SCAMP2 in the regulation of T-type calcium channel expression in the plasma membrane. Here, we show that similar to SCAMP2, the co-expression of SCAMP5 in tsA-201 cells expressing recombinant Ca_v3.1, Ca_v3.2, and Ca_v3.3 channels nearly abolished whole-cell T-type currents. Recording of intramembrane charge movements revealed that SCAMP5-induced inhibition of T-type currents is primarily caused by the reduced expression of functional channels in the plasma membrane. Moreover, we show that SCAMP5-mediated downregulation of Ca_v3.2 channels is essentially preserved with disease-causing SCAMP5 R91W and G180W mutations. Hence, this study extends our previous findings with SCAMP2 and indicates that SCAMP5 also contributes to repressing the expression of T-type channels in the plasma membrane.

KEYWORDS:

• Ion channels
• Calcium channels
• T-type channels
• Secretory carrier-associated membrane protein 5
• SCAMP5
• Channelopathy

List of abbreviations

Cav	=	Voltage-gated calcium channel
DAT	=	Dopamine transporter
Gmax	=	Maximal macroscopic conductance
NKCC2	=	Sodium-potassium-chloride cotransporter 2
Qrev	=	Intramembrane charge movement at the reversal ionic potential
Rack-1	=	Receptor for activated C kinase 1
SCAMP2	=	Secretory carrier-associated membrane protein 2
SCAMP5	=	Secretory carrier-associated membrane protein 5
SERT	=	Serotonine transporter
SNARE	=	Soluble N-ethylmaleimide sensitive factor attachement protein receptor
USP5	=	Ubiquitin specific peptidase 5

Acknowledgments

We thank Leos Cmarko for technical assistance.

Disclosure statement

No potential conflict of interest was reported by the authors.

Availability of data and materials

All data generated or analyzed during this study are included in this published article and its supplementary information files.

Authors’ contributions

E.R.M. and K.W. performed the electrophysiology and analyzed the data. N.W. designed and supervised the study. N.W. and E.R.M. wrote the manuscript. All authors critically revised the manuscript and contributed significantly to this work. All authors read and approved the final manuscript.

Additional information

Funding

N.W. is supported by a grant from the Czech Science Foundation (GACR #22-23242S) and the National Institute for Research of Metabolic and Cardiovascular Diseases (Program EXCELES # LX22NPO5104), funded by the European Union – Next Generation EU.